Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session FR: CEU Poster Session |
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Sponsoring Units: DNP JPS Room: Ritz-Carlton Hotel Ballroom Foyer 1:00pm - 3:00pm |
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FR.00001: High-resolution gamma-ray spectroscopy with a NASA/GSFC microcalorimeter at the Lawrence Livermore National Laboratory Greg Brown, Bret Beck, John Becker, Peter Beiersdorfer, Kevin Boyce, Rich Kelley, Caroline Kilbourne, F.Scott Porter, Andy Szymkowiak A 32 pixel laboratory microcalorimeter spectrometer built by the NASA/Goddard Space Flight Center and in operation at the Lawrence Livermore National Laboratory is now being used for gamma-ray spectroscopy. The second generation laboratory instrument, dubbed the XRS/EBIT, has been used to measure up to 60 keV gamma rays with a resolution of 60 eV or less. The microcalorimeter makes it possible to resolve many gamma-ray spectral ines for the first time. An overview of the operating parameters and measurement capabilities will be given, as well as example spectra. Work by the Univ. of California Lawrence Livermore Nat'l Laboratory was performed under the auspices of the D.o.E. under contract No. W-7405-Eng-48. [Preview Abstract] |
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FR.00002: Vibrational to Rotational Structure Evolution in Medium Mass Nuclei Mirela S. Fetea, Joe Hanley, Philip Pendleton A recently introduced empirical method is used to follow the evolution from vibrational to rotational structure in nuclei as a function of spin. EGOS (E-Gamma Over Spin) plots connect the relation between the gamma-ray energy and spin with the shape of the nucleus. In the E-GOS plots the trajectory for a vibrator decreases hyperbolically, while the trajectory for a rotor slightly increases to become almost flat for any higher spin. Results of the EGOS analysis for the medium mass transitional nuclei will be presented. The work was completed in collaboration with groups from the Wright Nuclear Structure Laboratory at Yale University, and from the University of Surrey, Guildford, England and was supported by the NSF Grant No. PHY 0204811 and Research Corporation Grant No. CC5494 [Preview Abstract] |
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FR.00003: Backbending phenomena in lightnuclei at A$\sim$60 mass region S. El-Kamessey, H. Alharbi, H Alhendi Recent studies of the backbending phenomena in medium light weight nuclei near A$\sim $60 expanded greatly our interest about how the single particle orbits are nonlinearly affected by the collective motion. As a consequence we have applied a modified version of the exponential model with the inclusion of paring correlation to describe the energy spectra of the ground state bands and/or the backbending phenomena in mass region at A$\sim $60. A firm conclusion is obtained concerning the successful validity of the proposed modified model in escribing the backbending phenomena in this region. Comparison with different theoretical descriptions is discussed. [Preview Abstract] |
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FR.00004: The Evolution of Vibrational to Rotational Structure in Nuclei Joe Hanley, M.S. Fetea, V. Nikolova For more than 25 years, phase and shape evolution that are ultimately related to the mechanisms by which atomic nuclei generate angular momentum have been major themes in nuclear structure research. In certain circumstances, the motions of the individual protons and neutrons making up the nucleus couple, give rise to collective vibrations or rotations of the nucleus as a whole. This presentation focuses on a new method to discern the nuclear evolution from vibrational to rotational structure in nuclei, as a function of spin. The E-GOS (E-Gamma Over Spin) plot is an empirical approach that describes the structure of the nucleus circumventing all of the parameters and model dependencies that had to be assumed in past research. The work was completed in collaboration with groups from the Wright Nuclear Structure Laboratory at Yale University, and from the University of Surrey, Guildford, England and was supported by the NSF Grant No. PHY 0204811, Research Corporation Grant No. CC5494 [Preview Abstract] |
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FR.00005: Charm study via electron-hadron azimuthal correlations in p+p and d+Au $\sqrt{s_{NN}}=200$ GeV collisions Sotiria Batsouli PHENIX data on single electron production indicate an excess of electrons over known light hadronic sources that has been attributed to open charm and beauty decays. The non-photonic electron yields are consistent with two different scenarios. One is the creation of a medium completely transparent to heavy quarks. The other is the creation of a highly opaque medium with the heavy quarks rescattering and hadronizing in the system. We can distinguish between these different scenarios by studying the electron-charged hadron azimuthal correlations with respect to the system size. The correlations in p+p and d+Au collisions provide a direct observation of the heavy quark jets and the baseline for possible shape modifications in the Au+Au central collisions. The method for extracting the non-photonic azimuthal correlations and the current results for p+p, d+Au at $\sqrt{s_{NN}}=200$ GeV PHENIX data will be presented. [Preview Abstract] |
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FR.00006: High percentage 3He polarizer using spectrally-narrowed external-cavity high power multi-array stack diode laser Michael Mason, William Hersman Parity-violating asymmetry experiments involving polarized slow neutrons, including the present NPDGamma experiment, require a large flux of polarized neutrons. Sources of neutrons from spallation targets moderated to cold temperatures provide a large amount of unpolarized slow neutrons. The unpolarized neutron beam can then be polarized by passing it through the polarized 3He cell, taking advantage of the greater attenuation of neutrons anti-aligned with the 3He than those that are aligned. The thickness of the up and down helium states determines the transmission of the down and up neutron states, and hence the transmitted neutron polarization and flux. Precision measurements of beta-decay asymmetries planned for the Spallation Neutron Source, including the abBA experiment, impose the additional requirement of small uncertainties in the neutron polarization. One way of accomplishing high precision in the neutron polarization is to force the neutron polarization close to unity by passing the neutron beam through many attenuation lengths of a thick polarized 3He spin-filter. The simultaneous requirements of high polarization, low uncertainty, and high flux demand the highest 3He polarization attainable. This can be accomplished with large volume cells by using our newly developed spectrally-narrowed external-cavity high power multi-array stack diode laser. [Preview Abstract] |
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FR.00007: Development of a Mossbauer Spectrometer Justin King, Michael Vineyard A Mossbauer spectrometer is being developed for use in an undergraduate experimental physics course and for research projects. A Co-57 provides 14.4-keV gamma rays which are detected with a krypton gas proportional counter. The source is mounted on an electromechanical drive that is operated in constant velocity mode using a Mossbauer drive controller. A circuit is being developed to operate the drive in constant acceleration mode so that Mossbauer spectra can be acquired with a multi-channel analyzer in a computer. Curricular materials are also being developed to use the Mossbauer spectrometer in the experimental physics course to measure changes in nuclear energy levels such as isomer shifts, hyperfine splitting, and quadrupole splitting due to an external magnetic field. [Preview Abstract] |
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FR.00008: Muon Backing Veto for UNCA Experiment at Los Alamos National Labs Shuang Du, Henning Back, Adam Holley, Robert Pattie, Chris O'Shaughnessy, Albert Young Muons are highly energetic charged particles originating form the upper atmosphere as a result of cosmic ray pion decay. Due to the muon's energies, they are very difficult to shield against and therefore register unwanted background in certain particle detectors. In our experiment the particle detectors are designed specifically to detect beta particles from neutron decay. To solve the muon background problem, thin plastic scintillator detectors are situated essentially flush with the back of the beta detectors. Cosmogenic muons pass through both detectors without stopping, producing a ``coincidence'' signal that is used to reject background. Wave-shifting fluorescent fibers direct light into a wire mesh photomultiplier tube (PMT). Wire mesh PMTs are insensitive to the magnetic field strengths present in our spectrometer detector, which approach 1 Tesla, and prevent normal PMTs from functioning. Our muon veto systems will be installed in the UCNA experiment in the summer of 2005. [Preview Abstract] |
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FR.00009: A desktop particle accelerator employing a pyroelectric crystal Jonathan Kalodimos, Rand Watson Pyroelectric crystals have long been known to generate large electric fields during a modest change in temperature. This effect is due to rearrangement of the crystalline structure which results in a large bound charge on the surface of the crystal. The bound charge and associated electric field are directly related to the temperature change, making large voltages possible. Due to the compact size of the crystal and the absence of a large power supply, pyroelectric crystals offer a potential means for developing portable particle accelerators and x-ray sources. It has been recently reported that using pyroelectric crystals to accelerate a deuterium ion beam into a deuterated target can produce D+D fusion. The objectives of the present work are to (a) verify the results of the D+D fusion experiments mentioned above, (b) optimize the conditions for particle acceleration, and (c) assess the possibility of extending this method to other nuclear reactions. [Preview Abstract] |
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FR.00010: Collisional Energy Loss of Energetic Particles Margaret Stewart RHIC has collided gold nuclei at 200 GeV per nucleon-nucleon pair. Upon a head-on collision about 10,000 particles are produced, a small fraction of them is energetic. However, experiments at RHIC have observed fewer energetic particles than expected from theory. This led to the conclusion that a new state of matter, possibly a quark-gluon plasma (QGP), is created in those collisions. When this hot and dense matter expands and cools down clustering into hadrons, the hadrons that are still energetic collide elastically and lose energy before reaching the detector. We have created a computer program that uses several physical concepts to simulate collisions between an incident energetic particle and hadrons in a thermal bath. This allows us to study the probability distributions of both the scattering angle and the energy of the incident particle after several collisions. That way, we will gain an understanding of the degree of collisional energy loss due to the late stage of hadron-hadron collisions, thereby quantifying the early stage energy loss of energetic particles in the created matter, which will give us a better understanding of the early universe. [Preview Abstract] |
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FR.00011: Beam Polarization Correction for Neutron-Deuteron Scattering Cross Section Kimberly Boddy, Taylan Akdogan, Maxim Chtangeev, Wilbur Franklin, John Hough, June Matthews An MIT-led collaboration has performed a measurement of the differential cross section for neutron-deuteron elastic scattering at the WNR facility of the Los Alamos Neutron Science Center. The linear accelerator provides an 800 MeV, unpolarized proton beam, which is directed toward a tungsten spallation source to produce beams of high energy neutrons. The neutrons are polarized due to spin-orbit interactions between the proton beam and the tungsten nuclei. In our experiment, a collimated neutron beam is incident on a liquid deuterium target, and the incident neutron energy is determined from time of flight information. The neutron-deuteron scattering cross section is measured by observing the scattered neutrons and recoiling deuterons in coincidence using an array of plastic and CsI scintillators. After a correction to the data to take the polarization of the neutron beam into account, the results are compared to previous nd and pd experimental results and to theoretical predictions that suggest the differential cross section at large angles is sensitive to a three-nucleon force. [Preview Abstract] |
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FR.00012: Search for Pre-Existing Delta States at BLAST from ${\bf{}^{2}D(e,e'\Delta^{++})}$ Chana Greene At the MIT-Bates Linear Accelerator Center a comprehensive study of low-Q$^{2}$ spin-dependent electron scattering from deuterium is being carried out using the Bates Large Acceptance Spectrometer Toroid(BLAST). This experiment has employed a polarized electron beam from the MIT-Bates linear accelerator incident on an internal polarized deuterium target and the BLAST detector. Deuterium's simple composition is an important factor in understanding the structure of the inter-nucleon potential. The pion production region has a resonant structure and is a promising location to search for pre-existing delta particles in deuterium. Theoretical calculations predict that delta resonant states account for anywhere from 0.25 to 3.60\% of the nuclear wave function more realistic predictions for deuterium range from 0.3 to 1.0 \%. We present here a preliminary report on the search for pre-existing deltas in the BLAST data. In the pursuit of this study Monte Carlo, data filtering and data quality techniques have been employed in order to ensure the best quality of data. [Preview Abstract] |
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FR.00013: Measurement of charge distribution of $^{16}$O through a C-foil for $^{4}$He($^{12}$C,$^{16}$O)$\gamma $ experiment at stellar energy Hisato Tanimoto Measurement of charge distribution of $^{16}$O passed through a C-foil is in progress at Kyushu University tandem laboratory so as to measure $^{4}$He($^{12}$C,$^{16}$O)$\gamma $ cross section at stellar energy by detecting $^{16}$O particles in a charge state. Downstream the helium windowless gas target, we put a thin C-foil to make the charge distribution of $^{16}$O equilibrium. Energy of $^{16}$O is 2-8 MeV, and existing data for the charge distribution of $^{16}$O in the energy range are different to each other by 15 {\%} at most. We measure simultaneously (1) the intensity of a $^{16}$O beam which is incident on a C-foil by counting $^{12}$C recoils by a Si-detector, and (2) the intensity of the $^{16}$O beam in each charge state by a Faraday cup downstream the C-foil. An electric deflector and a magnetic deflector are used to separate a $^{16}$O beam in a charge state from other$^{ }$beams in different charge states. [Preview Abstract] |
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FR.00014: Scintillation Light Detection Using VLPCs for a New Search of the Neutron Electric Dipole Moment Amber Nelson, Dipangkar Dutta, Haiyan Gao The electric dipole moment of the neutron(nEDM) is predicted to be on the order of 10$^-31$ e.cm. by the Standard Model. Currently, the experimental limit of this quantity is 6 x 10$^-26$ e.cm. Any non-zero nEDM is a direct violation of time-reversal symmetry, which may lead to a new understanding of CP violation. A new experiment has been proposed aiming at improving the current experimental limit by two orders of magnitude. A critical component of this new nEDM experiment involves detecting the scintillation light from the $\vec{n} + ^3\vec{He} \rightarrow$ p + t reaction at 300mK. A new light detection technique using a visible light photon counter(VLPC) is being developed for this experiment. The VLPCs are doped silicon based solid state photo multipliers with a high quantum efficiency and are normally operated at 6.5K. The scintillation light is wave-shifted from XUV to blue using deuterated tetraphenyl butadiene(TPB) and then to green using wavelenght-shifting(WLS) fiber. Over the summer, the bench set-up was constructed and preliminary results of these tests will be presented. [Preview Abstract] |
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FR.00015: In-Medium Effects and HBT ``Fireball'' Size in Ultraleativistic Heavy-Ion Collisions Laniece Miller, Ralf Rapp, Hendrik van Hees Standard equations of HBT interferometry determining the size of a fireball formed in heavy-ion collisions at RHIC do not easily match with experimental data. In a recent paper, G. A. Miller et al. have added an in-medium pion optical potential to help correct this discrepancy, resulting in a rather dense freeze-out configuration within their calculations. In the present project we investigate the effects of a more elaborate in-medium pion potential that more closely reflects the conditions expected for a fireball resulting from Au-Au collisions at RHIC. Modifying the potential alters the pion wave function, which in turn changes the HBT correlation. A computer code must be developed to handle the calculational complexities of both the pion wave equation and correlation function. The primary objective of this project is to determine the form and constants of an in-medium pion potential in connection with fireball conditions which more closely parallel the expected freezeout properties in heavy-ion collisions. [Preview Abstract] |
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FR.00016: Kell{\_}Wire Drift Chambers Anna Kell Wire Tracking Chambers are used to determine the track of charged particles through space. This project is to construct two multiwire proportional chambers, to write the data acquisition program to acquire data, and to track cosmic rays with the chamber system. The tracking chamber system will be used to test the efficiency and position resolution of other detectors placed between the tracking chambers. Information gained with these detectors will be used for the MECO and other experiments. The most prevalent cosmic rays at sea level are energetic muons, which are minimum ionizing particles. These particles are of most interest for our tests, thus muon signals are relevant for testing purposes. Drift chamber testing has revealed problems involving leakage currents across the detector frames which have been traced to the ``O'' ring seals. These have been replaced and the drift chambers are now being reassembled. The report of this project will present their operational parameters, including their efficiency, and tracking resolution as a function of voltage and gas. [Preview Abstract] |
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FR.00017: Monte Carlo Simulations of Type I X-Ray Bursts* Luke Roberts, Michael Smith, William R. Hix, Jacob Fisker Type I x-ray bursts (XRB) occur on the surface of a neutron star (NS) in a binary star system. Matter is accreted onto the surface of the NS and becomes extremely hot and dense. Once the envelope reaches a sufficiently high temperature, breakout from steady state CNO cycle thermonuclear burning occurs and a thermonuclear explosion powered by the $\alpha$p- and rp-processes ensues. Almost all reaction rates involved in theses processes have never been experimentally measured, and theoretically determined rates used in XRB models generally have large uncertainties. To understand how these uncertainties effect final nuclear abundances and energy generation throughout the burst, a Monte Carlo (MC) approach using a post-processing nucleosynthesis code is employed. In the MC simulation, all of the reaction rates are varied simultaneously and independently for each of 48,000 element synthesis calculations. The results are tested for significant correlations between specific reactions and final nuclear abundances. Preliminary results for one zone $-$ which reaches a peak temperature and minimum density of $1.02 \,GK$ and $1.166\times10^5 \,g/cm^3$ $-$ indicate that the rates of several positron decays, proton captures, and ($\alpha$,p) reactions, as well as $ \alpha(2\alpha,\gamma)^{12}$C, have significant correlations with many final abundances. Uncertainty estimates for predicted final nuclear abundances will also be presented. *ORNL is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR2275 [Preview Abstract] |
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FR.00018: Selective Population Shown by Five-Particle Transfer Reactions A.M. Crisp, N. Keeley, K.W. Kemper, O. Momotyuk, B.T. Roeder, M. Wiedeking, J. Liendo, F. Mar\'{e}chal, K. Rusek Spectra and angular distributions were obtained for the reactions $^{16}$O(d,p)$^{17}$O, $^{14}$N($^{7}$Li,$\alpha$)$^{17}$O, $^{14}$N($^{6}$Li,$^{3}$He)$^{17}$O, $^{12}$C($^{7}$Li,d)$^{17}$O, and $^{12}$C($^{6}$Li,p)$^{17}$O. Excitation functions were also measured for $^{12}$C($^{7}$Li,d) in the energy range 32-35 MeV and for $^{12}$C($^{6}$Li,p) in the energy range 26-32 MeV. These data were collected using the FSU Tandem/LINAC accelerator. Selective population of states in $^{17}$O was observed in each of these reactions, and the states populated in each reaction type did not vary with energy. This result indicates a direct, single-step transfer in each case. Further evidence for single-step transfer in the five-particle transfer reactions is provided by DWBA calculations performed on the selectively populated levels. In addition, characterization of particular $^{17}$O levels above 11 MeV will be presented. The most strongly excited state is at 11.82 MeV and its spin has been determined to be 7/2. [Preview Abstract] |
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FR.00019: Completeness of the Coulomb eigenfunctions Akram Mukhamedzhanov, Myles Akin Completeness of the eigenfunctions of the two-body Hamiltonian has been proved only for short-range interactions. In this work we present the first proof of completeness of solutions of the two-body Schr\"{o}dinger equation with repulsive Coulomb potential for arbitrary orbital angular momentum. We use Newton's contour integral containing the Coulomb Green function [1]. The proof is based on the analyticity of the Coulomb regular and singular solutions in the complex momentum plane. The most difficult part is to investigate the behavior of the integral around k=0. The presented proof allows one to apply the Berggren's method [2] to include resonant states into the complete set of eigenfunctions for particles interacting via the sum of Coulomb and nuclear potentials. It makes legitimate the usage of the so-called Gamow Shell Model [3] for nuclei with valent protons. The inclusion of the resonant states into the complete set calls for an extension of the Hilbert space, in which the norm of the resonant states is determined. We demonstrate that the scalar products containing the resonant states for charged particles can be well defined using Zel'dovich regularization factor. [1] R. G. Newton, J. Math. Phys. 1, 319 (1960), [2] T. Berggren, Nucl. Phys. A109, 265 (1968) [3] N. Michel et al., Nucl. Phys. A752, 335c (2005). [Preview Abstract] |
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FR.00020: Effect of quark momentum spread on hadron elliptic flow in relativistic heavy ion collisions Colin Young, Che Ming Ko In the na\"{\i}ve quark coalescence model, which allows for the coalescence into hadrons only of quarks with the same momentum, the elliptic flow of hadrons produced in relativistic heavy ion collisions would scale with their constituent quark content. Including the momentum distribution of quarks within hadrons is expected to lead to a violation of the quark number scaling of hadron elliptic flow. In a blast wave model, we have derived an analytical expression for the correction to the quark number scaling due to this effect and evaluated its value for heavy ion collisions at the Relativistic Heavy Ion Collider. [Preview Abstract] |
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FR.00021: Production Of Neutron-Rich Isotopes For Radioactive Ion Beam Development Abigail Gaddis, Andreas Kronenberg, Eugene Spejewski, H.K. Carter, Dan Stracener The Holifield Radioactive Beam Facility at Oak Ridge National Laboratory provides accelerated radioactive ion beams (RIBs) for nuclear structure and astrophysics experiments. Its ability to provide a variety of beams with sufficient intensity and purity for those experiments is necessary. Therefore, a continuing research effort exists to develop new beams and beams with higher intensity and purity. As a part of that effort, the goal of this project is to compare release yield data from the proton-induced fission of different actinide targets acquired experimentally using an on-line test facility. This facility includes a mass separator and uses the same target and ion source configuration as in the production of RIBs. Release data from targets such as uranium carbide are compared quantitatively by yields, chemical element by chemical element and isotope by isotope. After data analysis, a model function can be fitted to the data so that the results can be extrapolated to isotopes farther from stability. This model function takes into account differences in chemical behaviors and hold-up times. Comparisons from on-line tests with different actinide targets as well as the release data will be presented. [Preview Abstract] |
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FR.00022: Development of read-out electronics for time projection chamber (TPC) Asuka Saito, Shigeru Kiuchi A time projection chamber (TPC) is being developed for a cosmic ray test bench. The TPC (20*20*20cm, P10 gas, 5 micro seconds maximum drift) is used as 3D tracking device to determine the position and the angle of the incoming cosmic ray and has been tested with a proto-type readout electronics. The purpose of this R\&D is to build an electronic circuit that reads out full 8*9 (=72) signals from the TPC with 10 nano seconds sampling time and to evaluate the performance of the TPC. The electronic circuit is made up of pre amplifier, high speed flash analogue to digital converter (FADC), digital signal processor (DSP) with data storage memory, and computer interface. The circuit will be installed upon a printed circuit board for every 4 input channels. The TPC is triggered by external scintillation counter to read-out the data, the stored data will give 3D coordinates of hits along the trajectory after a calibration, then the charged particle tracks are reconstructed in order to investigate the position resolution and efficiency of the TPC and to be used for the cosmic ray test bench. [Preview Abstract] |
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FR.00023: Comparison between Simulations and Data for Neutral Meson Photoproduction on the Proton Fatima Mahmood, Michael Vineyard The photoproduction of $\pi ^{0 }$and $\eta $ mesons from the proton over an incident photon energy range of 0.5-2.3 GeV is being studied using data from the CLAS detector in Hall B at Jefferson Lab. This work is part of a systematic study of neutral meson photoproduction from the proton and light nuclear targets to investigate nuclear medium modifications of nucleon resonances and the meson-nucleon interaction. The $\pi ^{0 }$and $\eta $ mesons are reconstructed from their two-photon decay and from the $\gamma +p\to p+x$ missing mass. Monte Carlo simulations are being performed to determine the acceptance of the CLAS detector. The physics distributions generated from the simulations are being compared to those obtained from the data to tune the simulations. The analysis will be described and comparisons between the data and simulations will be presented. [Preview Abstract] |
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FR.00024: Hardware Upgrades to Increase Performance of Muon Tracking on PHENIX Dallas May After the proton-proton run of 2005, it was decided to implement a hardware upgrade for the higher luminosity runs of the heavy ions. By making the upgrades to low voltage distribution and the Glink/Clink crates of the Muon Tracker on the north and south arms, we increase the performance of the detector by decrease the down time needed for repairs. Each of these upgrades make it far easier and quicker to service individual circuit boards if and when they fail. These upgrades allow for increased uptime so that the most data can be acquired from the heavy ion collisions produced in RHIC. These collisions produce the very exotic J/Psi particles. These particles are desired for the exploration of the Quark-Gluon Plasma, which is believed to be the state of matter existing in the universe shortly after the Big Bang. [Preview Abstract] |
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FR.00025: Analysis of the Astrophysically Important $^{28}$Si($p,t$)$^{26}$Si Reaction J.A. Howard, R.L. Kozub, D.W. Bardayan, J.C. Blackmon, M.S. Smith, K. Chae, M.S. Johnson, K.L. Jones, S.D. Pain, J.S. Thomas, R.J. Livesay, D.W. Visser Study of $^{26}$Al in astrophysical environments is important to models of Galactic chemical evolution because the observation of this long-lived radioactive nucleus in the Galaxy indicates that stellar nucleosynthesis has occurred ``recently'' (in the last million years). However, the source of $^{26}$Al production in nature is still an open question, in large part due to uncertainties in the $^{25}$Al($p,\gamma$)$^{26}$Si reaction rate arising from a lack of information on the $^{26}$Si level structure above the proton threshold. To rectify this, the $^{26}$Si level structure was measured at the Holifield Radioactive Ion Beam Facility through study of the $^{28}$Si($p,t$)$^{26}$Si reaction. A 40 MeV proton beam was used to bombard a natural Si target, and the energy and angular distibutions of tritons were measured to reveal important $^{26}$Si level information. Details of the data analysis will be presented. [Preview Abstract] |
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FR.00026: Mathematically Modeling Accretion Discs around a Black Hole Nicole Sabbatino, Rebecca Surman A gamma ray burst is thought to occur when a massive, rotating star collapses on itself, and the energy released forms jets of very energetic photons. The outer layers of the collapsed star can form an accretion disc while the center forms a black hole. In order to understand this system fully, we must first gain an in depth understanding of the disc itself. We recalculate current accretion disc models to allow the exploration of a larger parameter space than currently available. We also investigate how the changing nuclear composition in the disc influences the disc's structure. The ultimate goal is to use this disc model to calculate the nucleosynthesis in the disc and in the outflows. [Preview Abstract] |
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FR.00027: Double-Beta Decay Studies of $^{100}$Mo to Excited 0$^{+ }$ States in $^{100}$Ru R.C. Remington, J.H. Esterline, M.F. Kidd, W. Tornow We are in the process of analyzing 1 kg x year of two-neutrino double-beta (2$\nu \beta \beta )$ decay data recently obtained at TUNL for $^{100}$Mo. Transitions to excited 0$^{+}$ states in $^{100}$Ru have half-life times which are at least one order of magnitude larger than those to the ground state of $^{100}$Ru. Our experiment features a 1kg sample of $^{100}$Mo placed between two HPGe detectors with a surrounding NaI annulus to veto background events. Passive shielding and coincidence techniques were used to minimize BG events. As the $^{100}$Mo nucleus double-beta decays to the first excited 0$^{+ } \quad ^{100}$Ru*, two gamma rays of 590.8 keV and 539.5 keV are subsequently emitted and detected in coincidence in our two HPGe detectors. We identified 15 (2$\nu \beta \beta )$ events for this transition, therefore, improving the statistical accuracy of the previously reported results of T$_{1/2 }$= 5.9$_{-1.1 }^{+1.7 }$x10$^{20}$ yrs of DeBraekeleer et al$^{2}$. We also give improved limits on T$_{1/2}$ for the transitions to the 2$^{nd}$ and 3$^{rd }$excited 0$^{+}$ states in $^{100}$Ru.\newline \newline Referenced: L. DeBraekeleer et al., Phys. Rev. Lett. 86, 3510 (2001) [Preview Abstract] |
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FR.00028: Coulomb Excitation of $^{50}$Mn and Isospin Symmetry in the $A=50$, $T=1$ Multiplet D.C. McGlinchey, J.W. Kremenak, L.A. Riley The $2_1^+$ of $^{50}$Mn has been studied using intermediate energy Coulomb excitation at 61 MeV/nucleon at the National Superconducting Cyclotron Laboratory at Michigan State University. Here a preliminary $B(E2:0^+_{g.s}\rightarrow2_1^+)$ value for $^{50}$Mn is presented. Using this result and $B(E2)$ values previously determined for $^{50}$Fe and $^{50}$Cr, a test of isospin purity in the Mass 50, $T=1$ multiplet is performed. [Preview Abstract] |
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FR.00029: Development of gain-matching algorithms for a Double-Sided Silicon Strip Detector David Simpson, Robert Grzywacz Proton radioactivity experiments almost exclusively employ the recoil-decay correlation technique which require the use of Double-sided Silicon Strip Detectors (DSSD) [Sellin]. Proper gain matching of detector strips, a basic requirement for such measurements, is of critical importance in ``fine structure'' experiments [KarnyPRL], where the uncalibrated strips could lead to artificial ``discoveries.'' Current gain matching techniques done manually on a strip by strip basis are time consuming and require a discrete source of radiation in which to line up the measured values. If performed during experiment, the calibrations interfere with the data taking time. New iterative methods of gain matching have been developed and tested using a computational algorithm that relies only on the requirement of the equality of particle induced signals on the front and back side of the silicon detector. This allows for faster gain matching, and can be used with any external radioactive source, even with continuous energy spectrum, like that generated by any particle radiation detected by the DSSD during the experiment. The algorithms were tested and bench-marked with data taken during recent proton radioactivity experiments at HRIBF. \newline References: \newline [Sellin] P.J. Sellin {\it et al.} Nucl. Instrum. Methods {\bf A 311}, 21 7 (2003).\newline [KarnyPRL] M. Karny {\it et al.} Phys. Rev. Lett. {\bf 90}, 012502 (2003). [Preview Abstract] |
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FR.00030: Improving Efficiency of Active Pixel Sensors through Digital Signal Processing Jeffrey Levesque, Howard Matis High energy nuclear collisions at the Relativistic Heavy Ion Collider (RHIC) produce an abundance of subatomic particles. STAR, one of four experiments at RHIC, currently has modest capabilities for detecting heavy flavor hadrons. By upgrading STAR with an active pixel sensor (APS) detector, we can significantly improve its ability to measure these short-lived particles. High detection efficiency for heavy flavor will allow measurements of quark thermalization and flow. This will lead to a better understanding of the hot, dense system of matter created in collisions, presumably quark-gluon plasma. Our group is investigating several algorithms and digital signal processing techniques to determine which are best for detecting minimum ionizing particles in APS data. We obtain actual noise data from prototype APS chips at expected leakage current levels, and then embed Monte Carlo charge distributions within the noise to simulate particle hits. Efficiencies of the signal extraction methods are quantitatively compared. We will present the results of these investigations. [Preview Abstract] |
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FR.00031: Kinematical analysis of $\Xi ^-$ hyperons stop event in KEK-E373 experiment Hiroyuki Nakamura The purpose of the E373 experiment is to study S=-2 nuclear systems with hundreds stopping events of $\Xi ^{-}$ hyperons. $\Xi ^{-}$hyperon is captured in the emulsion, interacts with a proton, and two $\Lambda $ hyperons are produced, in usual. In this experiment, we found NAGARA event that was identified as the production and decay of ${ }_{\Lambda \Lambda }^6 He$ among seven candidate events of double hypernucleus. We found several hundreds' events showing the emission of charged particles at the $\Xi ^{-}$ stopping points. Among them, there are two events having very characteristic decay topology. Only two charged particles were emitted from $\Xi ^{-}$ hyperon capture point, and one of those particles associated with an energetic charged particle. By the kinematical analysis, one event was identified as a non-mesonic decay of $\Lambda ^4 H$, and another one is probably a decay of $\Sigma ^-$ hyperon which is produced by week interaction between double strangeness. [Preview Abstract] |
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FR.00032: Modeling and Optimization of a Discrete Cos Theta Coil for a New Neutron Electric Dipole Moment Search Michael Betancourt The goal of the new neutron electric dipole moment experiment is to improve the limit on the current measurements of the neutron EDM by two orders of magnitude, resulting in the discovery of a finite EDM or the reduction of the limit on its value to the order of $10^{-28}$ e-cm. Ultra cold neutrons, produced via downscattering of 8.9 $\rm\AA$ cold neutrons from superfluid $\rm^{4}He$, will be bottled in static electric and magnetic fields where they will process at a frequency $\omega = (\mu_{n} B + d_{n} E) / J \hbar$. Neutron capture by surrounding $\rm^{3}He$ atoms produces scintillation light from which the neutron EDM can be extracted. Nonuniformities in the fields, however, induce a geometric phase in the neutrons that induces a false EDM signal. In order to minimize these errors, the uniformity of the fields, especially the magnetic field, must be optimized. To this end an analytical model of the discrete $\cos \theta$ coil that will generate the magnetic field for this experiment was developed and its validity tested with experimental measurements made on a prototype coil. Finally the model was used to optimize the final geometry of the $\cos \theta$ coil. [Preview Abstract] |
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FR.00033: Double-sided Silicon Strip Detector for the study of Double Hypernuclei II Takehiro Ishikawa The DSSD has an effective area of $64$ mm $\times$ $32$ mm, the thickness of 300 $\mu \textrm{m}$ and 50 $\mu \textrm{m}$ strip pitch. A number of strip-readout are 1280 channels in p-side and 640 channels in n-side, which correspond to 10 and 5 VA chips installed on the DSSD. We use a V550 C-RAMS (CAEN Readout for Analog Multiplexed Signals) ADC module as an ADC and a V551B C-RAMS module as a controller. In order to evaluate the performance of the DSSD in terms of the S/N ratio, we measured the pluse height distribution of $\beta$-ray passing the DSSD from a ${}^{90}$Sr source. We took about $100,000$ events data at variouse bias voltages, in order to check the depletion depth. At the bias voltage of $\pm 40$ V, we have obtained the S/N ratio as 33.76 $\pm$ 0.14 at p-side and 22.49 $\pm$ 0.09 at n-side for the minimum ionizing particles. The present results show the DSSD has sufficient S/N ratio to detect both $\Xi^{-}$ and $K^{+}$. [Preview Abstract] |
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FR.00034: Double-sided Silicon Strip Detector for the study of Double Hypernuclei I Takayasu Sekihara Double-sided Silicon Strip Detector (DSSD) has been designed for the study of double hypernuclei. This DSSD is a key detector in BNL- E964, which uses a new emulsion-counter hybrid method to find 10 times more double hypernuclei than before. In BNL-E964, $\Xi^{-}$ hyperons produced in the target (${}^{12} \textrm{C}$) by the $\textrm{K}^{-} + \textrm{'p'} \rightarrow \textrm{K}^{+} + \Xi^{-}$ reaction, are stopped in the emulsion and double strengeness nuclei are produced. The two DSSD's are placed within $5$ mm distance between the target and the emulsion. The DSSD is the best detector of tracking $\Xi^{-}$ because of its high position resolution and thinness which allows $\Xi^{-}$ passing the DSSD with minimum decay rate of $\Xi^{-}$. High position resolution of two DSSD's enables to trace the track of $\Xi^{-}$ with high scanning efficiency in the emulsion to find double hypernuclei. Design criteria and details of its construction are presented. [Preview Abstract] |
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FR.00035: High Energy Cosmic Ray Air Shower Events Studied through Radio Emission Michael Deaton One of the great mysteries remaining in astrophysics today is the unknown production mechanism of high-energy cosmic rays (HECRs). Since their initial discovery in the early 20th century, much greater energy cosmic ray events have been documented, some exceeding 10$^{20}$ eV. In 1962 G. A. Askaryan proposed that air showers of elementary particles produced by HECRs entering the atmosphere would emit a coherent radio signature (\emph{Sov. Phys. JETP} \textsf{14}, 441--443). The electronics available at the time, however, were largely incapable of handling such signals. Innovative research in this field is only recently possible with the advent of a new species of interferometric software radio telescopes. Within this category, the LOPES phased array (Low Frequency Array Prototype Station), operating within the range of 40--80 MHz, seeks to further study the processes of high energy cosmic ray air showers. The LOPES collaboration has recently reported a breakthrough correlation between HECR air shower events and predicted radio flashes as explained by so-called geosynchrotron radiation (Falcke, H. et al. \emph{Nature} \textsf{435}, 313--316, 2005). This presentation will briefly describe the LOPES project and the software development that was completed for \textsc{LOPES}--{\tt Tools}, the software package that is used for data analysis and mitigation of radio frequency interference for the LOPES project. [Preview Abstract] |
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FR.00036: Upgrades to the PHENIX Calibration Software Travis Hunter To ensure the greatest accuracy and precision of reconstructed data from the PHENIX detector at RHIC, periodic calibrations must be taken for each of its detector subsystems. Each of these subsystems contributes an integral part to our understanding of the very high density high temperature state of matter created in heavy ion collisions at RHIC. Any given calibration is only valid for a certain length of time, and then a new calibration must be taken. The storage of these calibration validity times is in a large database, which makes the task of verifying its integrity very tedious. We present a new graphical method of retrieving these data which makes the task of ensuring the appropriate calibrations are applied much easier and more reliable, thus improving the quality of the reconstructed data taken by PHENIX. We also present improvements to the low voltage control interface to the muon tracking subsystem that allow the logging of power cycles to its electronics in order to examine correlations between the calibration data from the muon tracker and power cycles of its electronics. [Preview Abstract] |
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FR.00037: Level 2 Filtering for the PHENIX Experiment at RHIC Austin Basye During the recently completed Run 5 of the PHENIX detector, located on the RHIC ring at BNL, the collaboration began recording data from the 200GeV polarized proton-proton beam. Throughout the run, multiple triggers were used to sort through the data to tag various rare probe events, such as a heavy di-muon event signifying the probable decay of a J/$\Psi $. The level 2 filters were primarily used to isolate these events from the raw data. This filtering system allowed the collaboration a unique opportunity to view the data emerging from the best polarized proton collisions to date in near-real-time. This is a definite advantage in that problems can be identified quickly and results can be produced within 48 hours of data-taking. Significant work was done with respect to the monitoring, maintenance, and improvement of this crucial subsystem which resulted in more efficient uses of resources. [Preview Abstract] |
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FR.00038: Coulomb Exertation of $^{46}$V and Testing Isospin Symmetry in the $A=46$, $T=1$ Multiplet J.W. Kremenak, D.C. McGlinchey, L.A. Riley A beam of the rare isotope $^{46}$V was studied via intermediate energy Coulomb excitation at 60 MeV/nucleon at the National Superconducting Cyclotron Laboratory (NSCL). $B(E2;0^+_{g.s.} \rightarrow 2^+_1)$ value of $^{46}$V was used to calculate the $M_o$ value for the nucleus. The extracted $M_o$ value in $^{46}$V was compared with the isoscalar multipole matrix element extracted from the previously determined $B(E2;0^+_{g.s.}\rightarrow 2^+_1)$ of $^{46}$Cr and $^{46}$Ti. Preliminary results will be presented. [Preview Abstract] |
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FR.00039: Gas gap optimization of MRPC Time-of-Flight detector for high-energy heavy ion experiment Yasuaki Takahashi The charged particle identification (PID) provides us an essential tool to investigate a hot and dense matter created in high-energy heavy ion collisions. Recently Multi-gap Resistive Plate Chamber (MRPC) has been proposed as a cost effective, a wide coverage, and a high resolution Time-of-Flight detector for PID. MRPC has similar timing resolution compared to a conventional scintillation counter with photo-multiplier tube and a large area MRPC is relatively inexpensive and the choice of segmentation of the MRPC is also flexible. MRPC is basically the stack of glasses as the resistive plates, and gap between the glasses are filled with the non-flammable gas. The electrodes and readout pads are located on the most outer glass surfaces on both sides. Among the various control parameters, the number of gas gaps in MRPC is one of the important key conditions to be determined the detector performance. In this research, the choice of size and shape of the read pad and the number of gaps of the MRPC are varied in order to optimize design parameters and operating conditions of the MRPC. The performance of the MRPC especially on the timing resolution is studied by a cosmic ray test bench with a good timing reference signal from trigger scintillation counters and with a good pointing position accuracy from tracking chamber. [Preview Abstract] |
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FR.00040: Production of $^{178m2}$Hf Isomeric Nuclei with High Energy Monoenergetic Neutrons M. Parker, A. Tonchev, B. Fallin, W. Tornow, A. Hutcheson, J. Kelley, J. Clark The 31-year high-spin isomeric state $^{178m2}$Hf (J$^{\pi }$= 16$^{+})$ provides an opportunity to study high-spin nuclear structure phenomena as well as future energy storage opportunities. Unfortunately, experimental data on its population via neutron induced reactions is very scarce. In order to study the yield of this isomer in the $^{179}$Hf(n,2n)$^{178m2}$Hf reaction, monoenergetic neutrons of energies 10, 12 14, 16, and 18 MeV from the TUNL tandem accelerator were produced and impinged on a $^{nat}$Hf target sandwiched between Al and Ag foils serving as monitors. The residual activity of the irradiated Hf and monitor foils was measured with a shielded HPGe detector. To provide better understanding of the population and decay of levels in Hf, complementary in-beam measurements of $\gamma $-ray emissions were also taken at E$_{n}$ = 12.5 MeV using BGO-shielded clover HPGe detectors. Analysis of these spectra allow the determination of the (n,2n) production cross sections of $^{178m2}$Hf. [Preview Abstract] |
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FR.00041: Simulations of effusion rates from generic ISOL target geometries Shankar Arul The objective of this study was to simulate the effusion of isotopes from proposed isotope separation on-line (ISOL) target geometries using the computer program SIMION. ISOL is one of two rare isotope production methods that will be used at the Rare Isotope Accelerator (RIA). Many short-lived radioactive species are produced in the ISOL target, and must be extracted rapidly to produce a useful radioactive beam. With SIMION, various ISOL target geometries were modeled to determine effusion times. By analyzing variations of the proposed geometry, we have determined the most efficient geometry that would provide the lowest effusion times to optimize extraction of short-lived species. The configuration that was found to be the most efficient was the one with the effusion space placed on the outer edge inside the target. [Preview Abstract] |
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FR.00042: Detector Characterization for a Parity-Violation Experiment Blair Cardigan Smith The G0 experiment at Jefferson Lab uses parity-violating elastic electron scattering to extract the strange quark contribution to the charge and magnetization distributions within the proton. The backward-angle phase of the experiment will begin acquiring data in December 2005. In this phase of the experiment, the trajectories of recoiling electrons will be reconstructed with plastic scintillator detectors. Aerogel threshold Cherenkov counters will be used for particle identification. Owing to the small asymmetries that must be measured in parity-violating experiments, the detectors function at a high rate and with high efficiency. Each detector must therefore be characterized in terms of light yield and timing resolution. Cosmic rays were used for this purpose, simulating the response to high energy electrons. Results of the calibration process will be presented. [Preview Abstract] |
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FR.00043: Angular distribution of the $^{4}$He($^{3}$He,$\gamma )$$^{7}$Be reaction Aliesha Anderson, Yannis Parpottas, Mohammad Ahmed, Richard Prior, Henry Weller The $^{4}$He($^{3}$He,$\gamma )^{7}$Be is key reaction in high energy solar neutrino production. A measurement of the gamma-ray angular distribution provides insight into the reaction mechanism and allows better extrapolation of the cross section to low energies. A gas cell experiment has been designed and built to study the angular distribution. This work reports on the design and construction of the gas cell and the gas handling system as well as energy loss measurements in the cell. The cell was designed to reduce the background due to beam interaction with the entrance and exit foils. The detector geometry was studied and calculated to optimize response and efficiency. Results of preliminary gamma ray measurements with a $^{3}$He beam will be presented. [Preview Abstract] |
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FR.00044: Determination of $^{13}$C($\alpha$,$\gamma$)$^{16}$O Reaction Rate at Stellar Energies Using Sub-Coulomb $\alpha$-transfer Reaction. Bert Green, Grigory Rogachev, Kirby Kemper, Brian Roeder, Simon Brown, Eric Johnson, Akram Mukhamedzhanov The reaction $^{13}$C($\alpha$,n)\&^{16}$O is considered to be the main source of neutron flux for s-process in AGB stars which produces roughly half of all the heavy elements in the universe. The rate of the reaction depends on the structure of the sub-threshold resonances, the most important of which is the 6.36 MeV 1/2$^{+}$ state. The spectroscopic factor of the state was measured using the $^{13}$C($^{6}$Li,d)\&^{17}$O reaction [1]. A surprisingly low value was obtained (S$_\alpha$=0.011). However, re-analysis of the data by N. Keeley et. al. [2] produced a spectroscopic factor which was over an order of magnitude larger. It is the goal of this experiment to resolve this conflict by using the same $^{13}$C($^{6}$Li,d)\&^{17}$O reaction, but at sub-coulomb energies. A reliable ANC approach can be used at this energy to extract the spectroscopic factor, avoiding uncertainty associated with nuclear potential. [1] S. Kubono et. al., Phys. Ref. Lett. 90 (2003) 062501-1 - 062501-4. [2] N. Keeley, K. W. Kemper, D. T. Khoa, Nuc. Phys. A 726 (2003) 159 - 172. [Preview Abstract] |
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FR.00045: Measuring $^{3}$He Cell Density Using a Tunable Laser Hannah DeBerg, Kevin Kramer, Haiyan Gao Compton scattering experiments using polarized $^{3}$He targets and the High Intensity Gamma Ray Source at the Duke Free Electron Laser Laboratory have been designed to investigate the spin polarizabilities of $^{3}$He and the neutron. The targets will consist of high-pressure $^{3}$He gas in glass cells that has been polarized by spin-exchange with optically pumped rubidium vapor. A precise knowledge of the number density of $^{3}$He in the cells is necessary for the experiments; however, the cells can neither be opened nor contain pressure sensors. The polarization technique requires a small amount of rubidium and N$_{2}$ in the cell along with the $^{3}$He. The width of the D1 and D2 absorption lines in rubidium are linearly related to the density of $^{3}$He gas in the cells. Observing this widening of the absorption spectrum is achieved by using a tunable laser controlled by LabView software and measuring the power transmitted over a range of wavelengths. Preliminary results will be obtained and analyzed before the end of the summer. [Preview Abstract] |
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FR.00046: Background Mitigation in a Highly-Segmented HPGe Detector M. Perry, A.W. Poon, R. Henning, K. Vetter, D. Campbell We present the first study of a highly-segmented HPGe detector with pulse shape discrimination in a low background environment. The detector consists of a 8x5 highly-segmented HPGe crystal, shielded with 5 cm of normal lead. Data was collected at the Oroville low-background facility to study backgrounds applicable to the proposed Majorana neutrinoless double-beta decay experiment. An analysis of the efficiency of highly-segmented detectors to eliminate these backgrounds will be presented. [Preview Abstract] |
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FR.00047: The Time of Flight Technique for Nuclear Lifetime Measurements Aaron Chester, Ryan Mckendree, Krzysztof Starosta, Wilhelm Mueller, Ana Becerril, Heather Olliver, Russ Terry, Chris Campbell, Jon Cook, Cristian Dinca The onset of deformation in even-even nuclei is known to be manifested by a decreasing energy of the 2$^{+}$ excited state, E (2$^{+}$), correlated with an increase in the associated reduced transition probability B(E2). It is surprising to observe for A$\ge^{110}$Pd nuclei that as E(2$^{+}$) decreases, so does B (E2). It is proposed to reinvestigate this trend using the time of flight technique, which is undergoing development at the NSCL. With this method, a fast beam of degraded nuclei of interest produced in a fragmentation reaction is Coulomb excited to the 2$^{+}$ state on a moveable target. A stationary degrader is positioned downstream to further slow the nuclei. Gamma-rays emitted during the de-excitation process before and after the degrader are measured at a different Doppler shift. The SeGA array of segmented germanium detectors is used for gamma-ray detection as it provides an optimal balance of sensitivity to changes in velocity and energy resolution. The ratio of intensities of the measured peaks yields information about the lifetime at the measured velocity. The results of a proof of principle experiment performed with the primary beam of $^{124} $Xe will be presented. [Preview Abstract] |
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FR.00048: Analysis Needs for Parity-Violation Experiment Alana Lajoie-O'Malley The G0 experiment at Jefferson Lab measures parity violating asymmetries in elastic electron-nucleon scattering to separately determine the electric and magnetic strange form factors over a broad range of Q$^{2}$. The next phase of the G0 experiment, performed at backward angles, will use two arrays of plastic scintillators, and aerogel Cherenkov counters to detect elastically scattered electrons. Two arrays are required in order to perform tracking and hence to differentiate between elastic and inelastic electrons. Fast scaler counting coincidences are read and cleared at the helicity reversal rate, giving rise to ``helicity-reversal'' events. In addition, ``detector-checkout'' events are acquired periodically to digitize pulse heights and timing spectra from the detectors. The detector-checkout events are essential for monitoring the performance of the detectors as well as individual photomultiplier tube (PMT) rates. For example, efficiency for electron detection and contamintions from backgrounds can be estimated using these events. In addition, aging of the detectors due to radiation damage is monitored. The most important aspect of the detector-checkout events will be that they will allow characterizing the success of the detectors to reject backgrounds. A custom C++ code converts raw data files into data summary files. The data summary files are analyzed using custom analysis tools (developed using the ROOT toolkit). The G0 analysis scheme will be discussed, with particular emphasis on detector-checkout events. [Preview Abstract] |
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FR.00049: Fabrication of CH$_2$ and CD$_2$ Targets for Radioactive Ion Beam Experiments N.D. Smith, J.A. Howard, R.L. Kozub, B.A. Schwer, M.S. Johnson, S.D. Pain, J.S. Thomas, D.W. Bardayan, J.C. Blackmon, C.D. Nesaraja, M.S. Smith CH$_2$ and CD$_2$ targets are used at the HRIBF at Oak Ridge National Laboratory for nuclear structure and astrophysics measurements with radioactive beams. The targets involved must be of uniform and specific thicknesses, chosen to optimize the yield and energy resolution of each experiment. A variety of film areas are needed to accommodate different experimental setups. We are therefore refining the target making process to achieve the greatest possible uniformity and precision. We are investigating the fabrication of target films from both polyethylene and polypropylene using organic solvents. Target quality is determined by measuring the energy loss of alpha particles as they pass through the target film. Using a position-sensitive silicon detector, both the positions and energies of the alpha particles are measured, enabling a thickness profile of the target to be created. Details of production and thickness measurements will be presented. \\ \\ Supported by U.S. DOE and NSF. [Preview Abstract] |
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FR.00050: Deformed rotational bands in $^{134}$Pr Stephen Padgett, Kris Starosta Highly deformed bands were first observed in the A=130 nuclei. For example, $^{132}$Ce attains highly deformed prolate shape with the major to minor axis ratio of 3:2. However, in $^{152} $Dy the first super deformed bands were found with an axis ratio of 2:1. Current work investigates the possible observation of highly- and super-deformed bands in $^{134}$Pr, which is an odd- odd neighbor of $^{132}$Ce. The nucleus of interest was studied via the $^{116}$Cd($^{23}$Na, 5n) reaction at beam energy of 115 MeV at the GAMMASPHERE facility. Five high spin bands were identified in $^{134}$Pr from thin target data, while quadrupole moment measurements are being performed for these bands through the DSAM analysis from the backed target data. The DSAM method provides information on nuclear lifetimes by combining average velocity at the moment of decay obtained from Doppler shifted $\gamma$-ray energies with modeling of nuclear stopping in the backing. The lifetimes in rotational bands are directly related to the quadrupole moment and nuclear shape and therefore reveal the degree of deformation for the investigated bands. [Preview Abstract] |
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FR.00051: Determination of Depletion Depths and Non-\-Uniformities in Thick Large Area Resistive Strip Silicon Detectors Mark Sikora, S.D. Pain, J.A. Cizewski, J.S. Thomas, K.L. Jones, D.W. Bardayan, J.C. Blackmon, M.S. Smith, J.M. James, R.J. Livesay, M.S. Johnson, R.L. Kozub, B.H. Moazen, C.D. Nesaraja High quality radioactive beams available at the HRIBF at ORNL enable the study of neutron-rich nuclei far from the valley of stability using (d,p) reactions performed in inverse kinematics. Obtaining data on nuclei in this region is important to our understanding of the development of nuclear structure away from stability, and is of interest to nuclear astrophysics. To perform these reactions requires proton detection with high solid angular coverage, with high resolution in energy and position. The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a silicon detector array under development, comprised of two rings of resistive-strip silicon detector telescopes. Alpha-particle tests on the thick (1000$\mu$m) prototype detectors have indicated regions of poor charge collection, present at near full-depletion bias voltages. However, such alpha-particles only penetrate $3\%$ of the thickness of the detector. Measurements currently being carried out with elastically scattered protons will test the detector response throughout its entire volume and will benchmark the dependence of the position resolution on the deposited energy in the $\Delta$E detector. The analysis of these measurements will be reported. [Preview Abstract] |
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FR.00052: Simulation of Cosmogenic Background's at Underground Facilities Kai Hudek, Alan Poon, Reyco Henning Fast neutrons produced by cosmic muons in rock surrounding an underground facility can generate irreducible backgrounds in detectors, and in some experiments determine the sensitivity. Understanding the muon-induced production and the response of underground detectors to fast neutrons is crucial for the design of next generation low background experiments. Simulations were conducted using the GEANT4-based Monte Carlo package MaGe, a joint development between the Majorana and Gerda collaborations. Simulations of the total muon-induced neutron background and spectrum as a function of depth, and the response of the proposed Majorana experiment will be presented. [Preview Abstract] |
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FR.00053: Development of techniques for off-line correction of non-linear signals from thin large area resistive-strip silicon detectors J.M. James, J. Livesay, S.D. Pain, J.A. Cizewski, M.A. Sikora, K.L. Jones, J.S. Thomas, D.W. Bardayan, J.C. Blackmon, M.S. Smith, B.H. Moazen, C.D. Nesajera, M.S. Johnson, R.L. Kozub The measurement of (d,p) reactions on heavy (Z$\approx$50) fission fragments, which yield information of interest to nuclear structure and astrophysics, are now possible using high quality radioactive beams, such as those at the HRIBF at ORNL. These reactions are necessarily performed in inverse kinematics which, along with the relatively low beam intensities, require the detection of proton ejectiles with large solid-angular coverage, a large dynamic range (between 1 and $>$10 MeV), and good resolution in energy and position. Particle identification is necessary at angles forward of $90^{\circ}$. To meet these requirements, the Oak Ridge Rutgers University Barrel Array (ORRUBA) is currently under development, consisting of two rings of large-area resistive-strip silicon detector telescopes. Tests on the prototype 140$\mu$m thick $\Delta$E detectors, using necessarily short shaping times, exhibit non-linearities in the signals due to the varying rise-times associated with the high capacitance and the large position-dependent resistance. Data are being obtained and analyzed, and techniques for performing off-line corrections of these position dependent non-linear signals are being developed. [Preview Abstract] |
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FR.00054: Modeling x-Ray bursts with New Nuclear Physics Karl Smith, Alex Brown, Jared Dunnmon, Alexander Heger, Emily Johnson, Alan Kruizenga, Thomas Rauscher, Peter Redl, Alexander Sakharuk, Hendrik Schatz, Michael Wiescher, Mark Wallace Multi-zone x-ray burst models simulate thermonuclear explosions on the surface of accreting neutron stars. The underlying nuclear reaction sequence in the x-Ray burst is the rp-process. We used an updated nuclear reaction network, in which we updated mostly rp-process reactions, in a one-zone model and observe its impact on x-Ray bursts, using the x-Ray light curve and final produced ashes. We also explored the validity of one-zone approximations as tools to investigate nuclear physics by comparing to a full 1D multi-zone model. [Preview Abstract] |
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FR.00055: Improving Energy Resolution for Neutron-Transfer Experiments at the HRIBF B.A. Schwer, J.A. Howard, R.L. Kozub, N.D. Smith, A. Kronenberg, M.S. Johnson, D.W. Bardayan, J.C. Blackmon, C.D. Nesaraja, D.C. Radford, M.S. Smith, J.A. Cizewski, K.L. Jones, S.D. Pain, J.S. Thomas, R.J. Livesay Theories of the formation of heavy elements by the $r$-process require information on neutron-capture reactions. To better understand these, (d,p) reactions using radioactive ion beams in inverse kinematics are being studied at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. In such experiments, the proton energy resolution is degraded by energy loss effects in the deuterated polyethylene (CD$_2$) targets. To improve the energy resolution, $\gamma$-rays in coincidence with the protons are detected with a segmented germanium detector array. While the $\gamma$-ray energy resolution is not affected by the thickness of the target, the energy spectrum of the $\gamma$-rays is Doppler broadened, because of the high velocity of the heavy recoil nucleus. GEANT simulations were performed to find methods of correcting for the Doppler effect with the segmented germanium detectors. A (d,p$\gamma$) test run using a 352-MeV $^ {88}$Sr beam with CD$_2$ targets of various thicknesses will soon be conducted at the HRIBF. The progress of this run and the results of the GEANT simulations will be presented. [Preview Abstract] |
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FR.00056: Using GEMINI to study multiplicity distributions of LCP's in heavy ion collisions Adil Bahalim, Joseph Natowitz, Seweryn Kowalski There is a multifragmentation process that occurs in heavy ion collisions. At sufficiently low densities and high temperatures, this process creates primary fragments that are usually in excited states. These primary fragments decay into secondary fragments while emitting light charged particles (LCP's) and releasing energy. Given the time frame of the decay, it is impossible to make direct experimental observations on the primary fragments; therefore, we must combine experimental observables from the secondary fragments with results from computer simulation programs, such as GEMINI, to reconstruct and identify the primary fragments and their conditions. This, in turn, gives us a better understanding of the nuclear equation of state. GEMINI calculates the decay of compound nuclei by sequential binary decays, until the resulting products are unable to undergo further decay. Decay simulations are run for nuclei with Z=3 to Z=40 at excitation energies from 2 to 5 MeV/amu at 0.5 MeV/amu intervals. At each excitation energy, 1000 events are simulated. The multiplicity distributions of each of the six LCP's in consideration (n, p, d, t, 3He, 4He) are extracted to ROOT from the data gathered by these simulations. The correlation between the mean multiplicity and the width of multiplicity distribution will be used in the reconstruction model input parameters. [Preview Abstract] |
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FR.00057: Exploring Neutron Dosimetry. John Keith Despite the relative difficulty detecting neutrons, there are several possible considerations we have to make when designing our neutron dosimeter. A polyethylene layer could be put to interact with neutrons to produce a proton or heavy ion which would then interact with a charged particle sensitive scintillator or have a scintillator directly sensitive to neutrons such as a liquid scintillator or one made of ZnS(Ag) doped hydrogenous plastic. This can then be put into connection with a phototube, or, as our choice was, a photocathode followed by an array of Gaseous Electron Multiplier (GEM) foils. The final component is the electronics readout catered to the specific application. We are going with a simple quad readout (4 squares of equal size) to determine the homogeneity of the incident neutron beam created in the 88-inch cyclotron at LBNL. This configuration consisting of ZnS(Ag) doped hydrogenous plastic, a photocathode sensitive to 450nm light (wavelength emitted by the scintillation), an array consisting of 4 GEM foils, and the electronics readout will be used for fast neutrons of about 14MeV. [Preview Abstract] |
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FR.00058: Modification of Magic Number through Mass Formula with Shell Correction Shinya Ito, Yuma Kikuchi, Akira Ohnishi, Kiyoshi Kato We study how single particle energies depend on the asymmetry of protons and neutrons. In most of former researches, single particle energies are not considered to be dependent on the asymmetry. In our research, the energy of each orbit is assumed to be a function of the asymmerty, (N-Z)/A. This assumption is based on the experimental fact that new magic numbers appear in neutron-rich nuclei[1]. We introduce this effect in a similar way to the shell correction by Myers and Swiatecki[2], and apply the correction to the Weizs{\"a}cker-Bethe mass formula. Energy levels are obtained by fitting to the nuclear masses at the ground state. Analyzing the obtained functions of single particle energies, we confirm the appearance of the new magic numbers which have been already indicated by the experiment, and find additional magic numbers at higher energy states. \\[1ex] References \\{} [1] R.Kanungo, I.Tanihata, A.Ozawa, Phys. Lett. B 528,58(2002). \\{} [2] W.D.Myers, W.J.Swiatecki, Nucl. Phys. 81,1(1966). [Preview Abstract] |
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FR.00059: Extracting the Eta Signal for Comparisions in Au+Au and Cu+Cu Collisions Karen Koop The Pioneering High Energy Nuclear Interaction Experiment (PHENIX) is an experiment collecting data from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratories. The goal of PHENIX is to study the Quark-Gluon Plasma, a new state of matter formed in the high energy densities created by the RHIC. PHENIX collected data in Au+Au, Cu+Cu, d+Au and p+p collisions at various energies. An interesting observation from the experiment has been the supression of neutral pions with high transverse momentum (pT) in central Au+Au collisions relative to expectations from proton+proton results. By comparing eta particle production to neutral pion production, the supression of particles can be evaluated for dependence on particle species. Comparisons of eta production can also be made between Au+Au and Cu+Cu reaction systems. In order to make these comparisons, the eta signal must be extracted. Techniques such as event mixing and background subtraction make this possible. As a participant in the Research Internships for Scientists and Engineers program, I had the opportunity to work with graduate students at the University of M\"{u}nster, Germany in their analysis of data taken from the PHENIX experiment. [Preview Abstract] |
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FR.00060: PPAC characteristics for unstable nuclear beams of intermediate energy II Kenichi Karatsu The parallel-plate avalanche counter (PPAC) is a detector that utilizes an ionization avalanche mechanism. We have constructed a model to explain the avalanche mechanism. Inside the PPAC, an electron is accelerated by a large electric field, which is present between the anode and cathode. Each time an electron travels its mean free path, colliding with a gas molecule, it loses all of its kinetic energy. With $n\left( x \right)$ as the number of electrons at position$x$, there are a few among them that do not collide at all; collecting enough energy to ionize a gas molecule. The number of such electrons is $n\left( x \right)\exp \left( {-l/\lambda } \right)$. While these electrons advance by$dx$, it collides with a gas molecule by a probability of $dx/\lambda $; liberating another electron. Therefore we obtain the relation \[ dn=n\exp \left( {-l/\lambda } \right)dx/\lambda \] This yields a relation similar to the empirical rule. In order to discuss the adequacy of this model, we must compare the parameters included in both equations. This calls for further testing of the operation of the PPAC with different gases and bias voltages. The experiments are being done at the tandem accelerator at Kyoto University. [Preview Abstract] |
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FR.00061: PPAC characteristics for unstable nuclear beams of intermediate energy I Shohei Okumura High-energy unstable nuclear beams produced by projectile fragmentation contain a variety of particles with a wide range of energy. Therefore, in elastic scattering experiments using unstable nuclear beams, the separation of inelastic processes is essential. The particles must be `tagged' by their momentum. For momentum analysis, we insert a position detector at the focal plane of the beam line spectrometer. The parallel-plate avalanche counter (PPAC) is a detector used to measure the positions of ion beams in the beam line. The PPAC is highly reliable and versatile in sense that its signals have extremely fast rise and fall times ($\sim $10$^{-9 }$sec) and that it can be applied to a wide range of energetic ions. As it is often used in low-energy experiments, the detection characteristics are well known in those ranges. Our objective is to reveal the yet unknown PPAC characteristics for unstable nuclear beams of intermediate energy. Our main interests are the detection efficiency, time and position resolutions, and their beam rate dependency, which are being tested with 6 GeV $^{20}$O beams at the National Institute of Radiological Sciences. [Preview Abstract] |
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FR.00062: Precision tests of calculated internal-conversion coefficients: the case of $^{134}$Cs W.E. Rockwell, H.I. Park, J. Goodwin, N. Nica, V.E. Iacob, J.C. Hardy Internal conversion coefficients (ICC) play an important role in nuclear decay schemes. Yet, the tabulated results of ICC calculations are only known to agree with experiment on average to within a few percent, and there are some cases of much more significant discrepancies. In particular, for transitions with energies close to an atomic-electron binding energy, the calculated ICC values depend strongly on how the theory deals with the hole left by the departing conversion electron. One approach assumes that it is filled instantaneously, while the other considers that it stays empty throughout the entire conversion process. To date there are few exact measurements of ICCs with an uncertainty below one percent and this lack of precision makes it difficult to be definitive about the validity of either theory. We are embarked on a program to rectify this situation. In our present experiment we aim to measure the K-shell ICC for the 128-keV E3 transition in $^{134}$Cs with a precision of one percent or better. The experimental value of its ICC, as currently evaluated, does not fit particularly well with any available theory [see S. Raman \textit{et al}, Phys. Rev. C 66, 044312 (2002)]. [Preview Abstract] |
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FR.00063: Gamma-Coincidence Modeling with MCNPX Jenna Deaven, Anne Emerson, Jamie Leiter, Sharon Stephenson, Kristen Toskes Tertiary neutrons produced in self-sustaining Inertial Confinement Fusion reactions can activate a carbon target through n + $^{12}$C $\to \quad ^{11}$C + $\beta ^{+}$. The subsequent positron-electron annihilations lead to .511-MeV coincidence gammas, and therefore the tertiary neutron yield can be determined by a gamma-coincidence detection experiment. Monte Carlo N-Particle eXtended transport code (MCNPX) is used to model the $^{12}$C experiment, and through a comparison with real data, the geometry for the detector system can be determined. MCNPX is also used to model the non-uniform neutron activation of the $^{12}$C. Results will be presented. [Preview Abstract] |
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FR.00064: Commissioning the Neutral Meson Spectrometer at the High Intensity Gamma-Ray Source (HIGS) for Photo-Pion Experiments. Dane Grasse, Mohammad Ahmed, Richard Prior, Henry Weller An experimental program to study pion-nucleon interactions at the upgraded High Intensity Gamma-ray Source (HIGS) at the Duke Free Electron Laser Lab is being developed. The pions are produced via the reactions, $\gamma $+p $\to \quad \pi ^{0}$+p and $\gamma $+p $\to \quad \pi ^{+}$+n, using polarized gamma rays. The Neutral Meson Spectrometer (NMS) and the Blowfish neutron detector array will be used to study the pion kinematics. This work reports on the calibration and testing of the NMS. The120 CsI crystals in the NMS were systematically gain calibrated using cosmic rays. The efficiency of a layer of scintillating veto detectors in front of the CsI array was analyzed by coincidence timing techniques. To test the system, the angular distribution of cosmic ray flux was measured. A Monte Carlo simulation was also performed for the $\gamma $+p $\to \quad \pi ^{+}$+n reaction to study the feasibility of $\pi ^{+}$ detection by the NMS. [Preview Abstract] |
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FR.00065: Initial Measurements of the Total Cross-Sections of the Reactions $K^-+p\to \Sigma (1385)+\gamma $ and $K^-+p\to \Sigma (1385)+\pi ^0$in the Crystal Ball Jason Summerlott The first ever measurements of the total cross-sections for the reactions, $K^-+p\to \Sigma (1385)+\gamma $ and $K^-+p\to \Sigma (1385)+\pi ^0$, are being determined for kaon momenta ranging from 514-750 MeV/c. These studies provide new insight into the states of excited Sigma and Lambda particles. Analysis is being done using data collected by the Crystal Ball Spectrometer in the AGS at Brookhaven National Laboratory. The Crystal Ball is primarily a photon detector, consisting of 672 NaI crystals. Kaons were incident on a liquid hydrogen target with the reaction final-state particles registering in the detector crystals. Charged particles were vetoed using plastic scintillators, thus restricting analysis to neutral particles. The primary background reactions for $K^-+p\to \Sigma (1385)+\gamma $ include $K^-+p\to \Sigma (1385)+\pi ^0$ and$K^-+p\to \Lambda +2\pi ^0$ ; these backgrounds, along with several others, were studied using GEANT Monte Carlo simulations. Measurements of the total cross sections for both reactions will be presented. [Preview Abstract] |
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FR.00066: Fiducial Cuts on CLAS for the E5 Data Set Kristen Greenholt The Thomas Jefferson National Accelerator Facility, in Newport News, Virginia, is home to CLAS (CEBAF Large Acceptance Spectrometer) which observes the scattering of an electron beam on a nuclear target. The acceptance of the detector is the ratio between the events we expect to observe in an ideal detector and the data that we actually measure with CLAS. In order to analyze data from regions of well-understood acceptance, we generated electron and proton fiducial cuts on CLAS, fitting a trapezoidal function to the azimuthal dependence in a particular scattering angle bin. Previously, we analyzed the 2.56-GeV, normal torus polarity data from the E5 run period. Our current analysis extends the method to the 2.56-GeV, reversed-torus polarity and the 4.23-GeV normal- polarity data sets of the E5 running period. We will compare the effects of fiducials cuts under these different running conditions. These results are consistent with our expectations, validating the use of fiducial cuts to isolate stable efficiency. [Preview Abstract] |
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FR.00067: Two-neutron transfer in the $^{6}$He + $^{209}$Bi reaction near the Coulomb barrier Patrick J. Mears, P.A. DeYoung, G F. Peaslee, J.J. Kolata, E.F. Aguilera, F.D. Becchetti The cross section for $\alpha $-particle emission in the $^{6}$He + $^{209}$Bi reaction at energies near the Coulomb barrier is remarkably large. Possible reactions that may produce the observed $\alpha $-particles include two-neutron transfer, one-neutron transfer, and direct projectile breakup. Each of these mechanisms results in a distinctive angular correlation between the $\alpha $ particle and the outgoing neutron(s). A neutron-$\alpha $-particle coincidence experiment was performed to study two-neutron transfer to unbound states of $^{211}$Bi. It is shown that approximately 55{\%} of the observed $\alpha $-particle yield at and beyond the grazing angle is due to this process. This is more than 2.5 times the fraction attributable to single-neutron transfer. This work has been published: Phys. Rev. C 71, 051601 (R) (2005) [Preview Abstract] |
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FR.00068: Momentum Corrections for the E5 Data Set Robert Burrell The Thomas Jefferson National Accelerator Facility located in Newport News, Virginia, is home to the CLAS (CEBAF Large Acceptance Spectrometer) detector, which measures scattered particles from high-energy collisions of an electron beam and a nuclear target. Initial measurement of the momentum of charged particles is done by reconstructing tracks using different detecting elements and a toroidal magnetic field. To improve these momentum measurements, we apply corrections. The quantity qB/p (q is charge, B is proportional to the magnetic field, and p is momentum) is extracted from elastic ep scattering using tracking and also from the well-measured electron and proton scattering angles. The difference between the two quantities is parameterized to determine the correction factors. We previously applied this technique to the 2.56 GeV normal torus polarity data set of the E5 run period and now will be presenting the results from the other E5 data sets. [Preview Abstract] |
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FR.00069: Drift Chamber Development for PHENIX Muon Trigger RPC Tests. Aaron Veicht The PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory will measure the flavor dependent quark and anti-quark polarizations in the proton. In proton-proton collisions a quark and anti-quark interaction can be signaled by the formation of a W-Boson. Experimentally in PHENIX, W- Bosons are detected through the presence of a high energy muon. The PHENIX detector presently triggers muons above 2 GeV, including those from meson decays. This trigger condition results in a data flow ten times higher than the available data acquisition bandwidth in PHENIX. We propose to introduce fast first level trigger counters for an on-line measurement of the muon momentum. With this upgrade in place, a trigger condition of muon momenta greater than 10 GeV will decrease the data rate by a factor of twenty. The proposed first level muon trigger will rely on technology developed for the CMS detector at LHC. Application of the CMS RPC's in PHENIX will require an improvement in position resolution. In this paper we present the design, simulation and construction of a drift chamber package to be used in the PHENIX RPC cosmic ray test stand. [Preview Abstract] |
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FR.00070: Investigation of Hyperon Polarization in Preparation for ATLAS Lambda-b Data Sarah Lumpkins, Homer Neal The fact that inclusively produced hyperons are produced with significant polarization was first discovered at Fermilab about thirty years ago. This field of research has seen much experimental work since then, although theoretical understanding is still lacking. One mystery in particular that has eluded explanation is the shape of the lambda polarization vs. transverse momentum curve; the lambda polarization grows to a sizeable negative value for p{\_}t up to around 1.0 GeV/c and then plateaus for the next 2 GeV/c. Currently, there are no polarization models which have been able to successfully account for all known hyperon polarization phenomena. My project surveys all high energy hyperon polarization data in an effort to develop a model that provides a comprehensive explanation of the data. Initial results of this project support a quasi-classical parton-parton scattering model in line with that developed by Neal and Nielsen in 1974 in explanation of high energy elastic proton-proton scattering data. This analysis of lower mass hyperons is crucial in preparation for anticipated data on lambda-b hyperon polarization in ATLAS; due to the much larger mass of the lambda-b hyperon, certain physical models predict even larger polarization effects for the lambda-b. Thus, future lambda-b studies have an even greater potential for providing insight into fundamental processes of nature. [Preview Abstract] |
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FR.00071: Design, Construction and Test of Resistive Plate Counters for the PHENIX Muon Trigger Yongsun Kim Polarized proton-proton collisions used in the PHENIX experiment at Brookhaven National Laboratory's Relativistic Heavy Ion Collider will accurately determine the spin contribution of quarks and anti-quarks to the proton spin. Sensitivity to quark and anti-quark polarizations arises in W-production which experimentally is characterized by the detection of high momentum muons. The effective cross section (including PHENIX acceptance) for W-production is about 1 nb and collision rates of 10 MHz are required to accumulate sizable W-boson samples. The high collision rate requires an upgrade of the PHENIX muon trigger system. It was decided to use RPC's as dedicated first level trigger detectors. RPC's are fast detectors, simple in structure and cheap in construction. The PHENIX RPC design is based on the CMS muon trigger RPC's. Before constructing large scale RPC's at PHENIX, prototype RPC's of several designs will be tested using test beam and cosmic ray muons. We present our work to improve the position resolution of the CMS- designed RPC's and our results on RPC efficiency, timing resolution and rate capabilities. [Preview Abstract] |
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FR.00072: Forward Calorimeter for the Compact Muon Solenoid Aduramigba Sopeju, Christopher Cowden, Mario Spezziga, Nural Akchurin In 2007, the Large Hadron Collider (LHC) at CERN in Geneva would be turned on and then used to study the collision of protons and lead ions at extremely high energies. The purpose of these high energy collisions is to study the origin of mass and recreate the conditions of the first few moments of the universe. The Compact Muon Solenoid (CMS) is one of the experiments at LHC. I am presently working on the Forward Calorimeter (HF) of the CMS. Electrons, Photons and hadrons would be stopped by the calorimeters allowing their energies to be measured. The Calorimeter is made up of very sensitive materials mostly thin quartz fibers embedded in blocks of steel. The particles shower in the blocks and produce Cherenkov radiation in the optic fibers. This provides an energy measurement for both particles interacting electromagnetically and hadronically. The current goal for this calorimeter is to increase the forward coverage of CMS, improving the measurement of transverse energy, especially for high energy forward jets, which are a signature of some important physics processes [Preview Abstract] |
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FR.00073: A New Experiment to Study Transverse Proton Spin Structure through the Drell-Yan Process in Polarized Proton Collisions at RHIC Hye Ryong Kim Over the past 30 years, significant progress has been made in understanding longitudinal proton spin structure through polarized deep inelastic scattering experiments at SLAC, CERN, DESY, and Jefferson Laboratory. In contrast, the helicity flip transversity distributions of quarks inside a transversely polarized proton are completely unknown. Novel accelerator techniques developed at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory make it possible to study transversity through the Drell-Yan process in high energy polarized proton-proton collisions. An initial study by Vogelsang et al. showed that measurement of spin asymmetries in Drell-Yan at RHIC will only have poor statistical resolution. Based on simulation studies using the event generator PYTHIA, we will demonstrate that the RHIC luminosity upgrade with electron cooling and special focusing magnets (RHIC II) in combination with a new large acceptance calorimeter will lead to precise measurement of transverse single and double spin asymmetries, and thus the transversity quark distributions. [Preview Abstract] |
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FR.00074: Thermal Analysis of Heavy Ion Collisions Laura Stiles At Brookhaven National Laboratory, the Relativistic Heavy Ion Collider accelerates heavy ions and protons to relativistic speeds to create extreme condition collisions. Detectors study these collisions, the ultimate goal being the study of a new form of matter, the quark-gluon plasma. One of the detectors, BRAHMS, or the Broad Range Hadron Magnetic Spectrometer, measures only a small number of particles, but over a wide range of momentum and angles. One question being studied is if different regions of the hot partonic matter created in these collisions loose causal contact with each other before they reach chemical equilibrium. A thermal model package, THERMUS, has been created that can be run in the object oriented data analysis framework, ROOT. THERMUS is a C++ implementation of the grand canonical ensemble, where charge, baryon number and strangeness are conserved on average. BRAHMS data of the ratios of different particles produced in collisions, are entered in, along with six parameters, chemical freeze out temperature, baryon number, strangeness and electric chemical potentials, fireball volume, and saturation factor. When the other parameters are given fixed values, T, muB, and muS are fit to the lowest value of chi square. The results from THERMUS show that as we move to more forward angles, both the strange quark chemical potential baryochemical potential increase. We will compare our results to lower energy data from recent RHIC runs and experiment NA49 at CERN. [Preview Abstract] |
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FR.00075: Determining the effect of magnetic fields on the relative biological effectiveness of gamma rays Beverly Lau, Frederick Becchetti, Yu Chen Experiments at the Phoenix Memorial Labs were done to compare the effect of an 8.9 kCurie Cobalt-60 source on Saccharomyces cerevisiae (baker's yeast) with and without a 0.78 Tesla magnetic field. At a distance of 30 centimeters from the source, the yeast cells were irradiated with a dose rate of 56 kRad per hour, and doses of 20 and 30 kRad were sufficient to produce a survival rate of 50 percent or less. It was discovered that the magnetic field causes the relative biological effectiveness of incident gamma rays to change slightly. Successive trials of this experiment have shown reproducible effects. [Preview Abstract] |
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FR.00076: Electron Identification in the EEMC at STAR Joshua Vredevoogd, Theodore Hopkins The Endcap Electromagnetic Calorimeter (EEMC) at STAR provides a new tool to probe the origins of nucleon spin. In particular, the spin contribution of up and down sea antiquarks can be studied through charged intermediate vector boson (W) production in quark-antiquark annihilation. The W bosons are identified in STAR by the observation of a single electron track from their decay. By measuring the parity-violating helicity sensitivity of the yield of these electrons, one can infer information about spin preferences of sea antiquarks in the proton. A prerequisite for this, and several other studies, including J/Psi production, is the ability to efficiently differentiate between electrons and hadrons as they pass through the calorimeter. Measurements of the transverse and longitudinal evolution of the electromagnetic and hadronic showers in the EEMC provide distinguishing characteristics that permit the separation of these two shower types. We have developed an algorithm that provides electron identification and charged pion background suppression that surpasses the design requirement for EEMC signals alone. Further efforts are underway to discriminate against prompt photon and neutral pion backgrounds, both of which also produce electromagnetic showers in the EEMC. An overview of our identification method and results are presented. [Preview Abstract] |
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FR.00077: Angular Distribution of Gamma Rays in Neutron-Rich Hafnium Nuclei Steven Sheppard The HISPIN research group at UMass Lowell conducts \underline {H}eavy \underline {I}on \underline {Sp}ectroscopic \underline {I}nvestigations of \underline {N}uclei to learn about the physics of nuclear rotation. In this experiment, performed at the 88'' Cyclotron at Lawrence Berkeley National Lab, a 750 MeV beam of $^{136}$Xe was incident upon a $^{180}$Hf target in order to excite $^{180}$Hf nuclei to high angular momenta. Gammasphere, an array of 110 Compton-suppressed germanium detectors, with CHICO (\underline {C}ompact \underline {H}eavy \underline {I}on \underline {Co}unter), a large solid-angle, position-sensitive, heavy-ion detector, was used to record, in multi-parameter event mode, the recoil angles, flight times and gamma emissions of the nuclei. This allows event-by-event Doppler correction for the gamma rays, to restore the intrinsic detector resolution in the spectra. The gamma-ray angular distribution was measured with respect to the direction of both the beam and the recoiling nucleus, using the CHICO data to identify the flight path. These angular distributions can identify the nature of the transition responsible for a characteristic gamma emission, and yield knowledge of the excited level structure of a nucleus and the governing physics. [Preview Abstract] |
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FR.00078: Determination of Energy Loss of 3-MeV alpha particles in Ni foil and $^{3}$He Gas Using a Mg($\alpha $, $\gamma )$ Resonance K.P. Michnicki, C. Bordeanu, J.D. Lowrey, K.A. Snover, D.W. Storm The largest nuclear physics uncertainty in calculating the neutrino flux from the sun is presently in the value of $^{3}$He +$^{4}$He S-factor. The cross section will be measured for alpha particles incident on a gas cell filled with $^{3}$He. The cross-section for this reaction depends on the energy of the alpha particles. As the alpha particles pass through the $^{3}$He gas cell, they lose energy, both in the foil window and in the gas. In order to minimize uncertainty in the measurement of S$_{34}$(0), it is important to understand the energy distribution at different locations in the gas chamber. Excitation functions for the $^{24}$Mg($\alpha $, $\gamma )$ resonance at 3.1998MeV were obtained for various gas pressures and beam currents as well as without the gas and foil. By analyzing the excitation functions, we determine the separate energy losses in the foil and gas. We also measured the dependence of the energy loss on the beam current, thereby finding the effect of beam heating on the density. From the observed resonance width, we determined the total beam energy spread, due to straggling and foil nonuniformity. [Preview Abstract] |
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FR.00079: Development and Benchmark Studies of the Indiana Rf Photocathode Source Simulator* Daniel Bolton, Chong Shik Park, Mark Hess The Indiana Rf Photocathode Source Simulator (IRPSS) code is being developed to calculate the electromagnetic fields created by an electron beam in a photoinjector, and to simulate the effects of these fields on the beam using time-dependent Green's function methods. In this poster, we show initial IRPSS simulation results for a simplified photoinjector geometry consisting of a semi-infinite cylindrical pipe and cathode using the experimental parameters for the BNL 1.6 GHz photocathode gun [1]. We also show the excellent agreement within a benchmark study between the IRPSS code operating with the same simplified geometry and the analytical solution for a disk-like bunch and its ``image'' bunch propagating with uniform velocities in opposite directions with free space boundary conditions. Our benchmark study has demonstrated that the effects of self-fields reflecting from the pipe, as well as the electromagnetic shock fronts due to causality conditions, may be significant in understanding the physics of photoinjectors. *This research is supported in part by the NSF REU program. [1] K. Batchelor et al, ``Development of a High Brightness Electron Gun for the Accelerator Test Facility at Brookhaven National Laboratory'', EPAC'88, Rome, June 1988. [Preview Abstract] |
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FR.00080: Total cross section of Single-Quantum Annihilation Yushi Tsubota, Syogo Ida, Sachio D. Imabeppu Positron annihilation with electron usually produces two 511 keV photons in a final state. There were intense experimental studies on the two and more photons in the final states although little studies have been carried out on a single-quantum annihilation (SQA). Here we report an experimental study of SQA. When an electron is bound in a nucleus, momentum can be carried away by the nucleus and SQA is allowed. There are theoretical and experimental studies on the dependence of positron kinetic energy and target atomic numbers (Z) where energetic positrons were used for the study. We carried out an experiment to search for SQA by a positron provided by a radioactive positron source of 22Na. We have low energy ($\sim$ 100 keV) positron and SQA spectrum represents and initial positron energy and binding energy of atomic electron with which the annihilation takes place. We discuss mechanism of SQA based on observed event rate and SQA energy spectrum. [Preview Abstract] |
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FR.00081: A 3D Liquid Scintillator Neutrino Detector Daniel Passmore, Rex Tayloe The Fine-grained Intense Neutrino Scattering Scintillator Experiment (FINeSSE) is a proposed liquid scintillator detector that will measure track coordinates in 3D using WLS optical fibers. FINeSSE proposes to use high intensity charged and neutral current neutrino scattering to precisely measure the strange quark spin component, delta s, of the nucleon. A FINeSSE 1D prototype was measured using the 200MeV proton beam at the Indiana University Cyclotron Facility (IUCF). Results for position and angular resolution of charged particle tracks measured in this device will be presented. [Preview Abstract] |
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FR.00082: $\phi $ meson production in Deuteron-Gold Collisions at $\sqrt s =200$ GeV at PHENIX Sungho Yoon Surprising nuclear effects from $J/\psi $ and light meson productions at forward rapidity region have been observed in d+Au collisions at $\sqrt s =200$GeV in PHENIX using the forward muon spectrometers. The $J/\psi $ signals were reconstructed through the dimuon decay channel, and the light mesons ($\pi $,$K)$ were detected through their decays to muons as well as through the `punch-through' hadrons. To understand the origin for the nuclear effects, it would be very useful to detect the $\phi $ meson which contains a pair of strange and anti-strange quarks. The measurement of $\phi $ production at PHENIX will also help us to understand the nuclear effects as a function of the mass of the produced hadrons. The $\phi $ production could be measured via $\phi \to \mu ^+\mu ^-$ decay channel using the muon spectrometers at PHENIX. However, the current trigger system is optimized for the measurement of $J/\psi $. An improvement to the trigger system will allow the study of $\phi $ production. We have calculated the production of $\phi $ in the d+Au reaction at $\sqrt s =200$ GeV. The acceptance of the PHENIX detector for the $\phi $ events, and the kinematic coverage and the anticipated statistical accuracy for the accepted $\phi $ events have also been studied. In this talk, we present the results of this study. [Preview Abstract] |
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FR.00083: Excited States in the Nucleus $^{73}$Br Rafael Yah, Susan Fischer, Kim Lister The nucleus $^{73B}$Br was produced in the reaction $^{40}$Ca ($^{36}$Ar,3$p$) using the ATLAS accelerator at Argonne National Laboratory. Gamma rays from the decay of excited states in this nucleus were detected by the Gammasphere array, and the recoiling nuclei were identified according to mass at the focal plane of the Fragment Mass Analyzer. Gamma-gamma coincidence data gated by mass have been analyzed. Prior to this work, three rotational bands were observed in $^{73}$Br, and later extended to high angular momentum. The current study has identified several additional rotational bands which begin at low angular momentum and excitation energy. The new bands will be compared with the known band structures in $^{75}$Br and $^{71}$Br. [Preview Abstract] |
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FR.00084: Gas-Filled Recoil Separation of Heavy Ions at Intermediate Energies Matthew Sternberg Current capabilities for the capture of fusion products produced at the Argonne Tandem Linear Accelerator System (ATLAS) and used for mass measurements at the Canadian Penning Trap are limited. The facility can capture reaction products emitted at angles up to 4 degrees off axis. In many reactions that take place the majority of recoil products are emitted at angles within 4 degrees of the axis. However, there are many desirable reactions where the majority of products fall outside this window. The use of a large bore solenoid magnet has been investigated as a means of capturing a larger range of recoil products. A Monte Carlo simulation was developed to model the transport of ions through a gas-filled solenoid magnet and different means of disposing of the primary beam have been investigated. A method was developed in which a large range of recoil products at various energies could be efficiently separated from the primary beam. Simulations suggest that recoil products could be captured at angles as large as 12 degrees, improving the current efficiency by as much as 1000{\%}. Design and construction of the proposed apparatus are currently underway at Argonne National Laboratory. [Preview Abstract] |
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FR.00085: Drell-Yan Measurements of Nucleon and Nuclear Structure with the FNAL Main Injector Donald Isenhower, Rusty Towell, Michael Sadler Work preparing for Fermilab E906 will be reported. This experiment is a continuing development of the Fermilab E866/NuSea Drell-Yan experiment that determined the light anti-quark asymmetry in the proton. In the Drell-Yan process, a quark (anti-quark) in the beam hadron annihilates with an anti-quark (quark) in the target, which produces a lepton pair. Thus the D-Y interaction is able to probe the sea quarks. E906 will significantly improve the results above Bjorken x of 0.2, where statistics were limited in E866/NuSea. Using the Main Injector at Fermilab at 120GeV/c, an improvement of a factor of 50 will be possible. [Preview Abstract] |
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FR.00086: Target Thickness Optimization of $^{12}$C for Tertiary-Neutron Activation at OMEGA Kristen Toskes, Anne Emerson, Jenna Deaven, Jamie Leiter, Lauren Kate McNamara, Sharon Stephenson One way to determine the $\rho $R (areal density) of IFC capsules is through tertiary-induced neutron activation of elements with appropriately high thresholds such as $^{65}$Cu or $^{12}$C. Since the tertiary neutron yield is many orders of magnitude lower than the primary yield, the experiment demands modeling to determine the optimal target thickness. Codes such as MCNPX seem well suited for such a project; however, activation eventually causes gamma-coincidences, which cannot be ``tallied'' in MCNPX. MCNPX can be used to provide particle track information for a known geometry for \underline {single} gammas. External coding is utilized to fabricate pairs (i.e. coincidences). This allows for the determination of the transmission of both gammas in varied thicknesses of $^{12}$C. The optimal thickness depends on the solid angle, the activation, and the attenuation factor appropriate for each gamma. Results will be presented. [Preview Abstract] |
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FR.00087: Quadrupole moment of the $\gamma$-soft $^{196}$Pt E. Novitski, V. Werner The $^{196}$Pt nucleus is considered to be one of the best examples of the O(6) $\gamma$-soft symmetry in the Interacting Boson Model (IBM) based on energies and B(E2) values, especially the $2^+_2 \rightarrow 0^+_1 / 2^+_2 \rightarrow 2^+_1$ B(E2) ratio, which is close to the O(6) limit of 0. However, the quadrupole moment of $^{196}$Pt (and that of neighboring $^{194}$Pt) is known to be positive and sizeable, which hints at a considerable oblate deformation of the nucleus. It is impossible to describe the O(6)-like features and the nonzero quadrupole moment simultaneously within the commonly-used consistent-Q formalism in the IBM-1, in which the same quadrupole operator is used in the Hamiltonian and the E2 transition operator. Therefore, IBM-1 calculations were performed breaking the consistent-Q formalism. An alternative approach was taken in the proton-neutron version of the IBM (IBM-2), choosing different parameters for the proton and neutron quadrupole operators, thus introducing triaxiality by different deformations of the proton and neutron bodies. Work supported by US DOE grant number DE-FG02-91ER-40609 and the Perspectives on Science Program of Yale University. [Preview Abstract] |
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FR.00088: Is Gravity a Long-Range Manifestation of Short-Range Nuclear Forces? Shantilal Goradia Consistent with Einstein's paper (1919), I propose gravity is a long-range manifestation of nuclear forces, too tiny to be detected beyond short-ranges by particle accelerators (physics/0210040). The implicit ``strong gravity'' at the edges of slits in double slit experiments would impact the curved space-time, and subsequently, the entire network of geodesics downstream of the slits as a function of the number of OPEN slits. This makes the screen pattern a function of the number of open slits, independent of a particular slit or the total number of slits selected to shoot the photons. My proposal may also explain the quantum uncertainty. The quantum wormholes in my later proposal (www.gravityresearchinstitute.org) between the ``observed'' particles and we, ``observers'', impact the information passing through them by combining their attributes of quantum time ($\Delta t)$ and quantum energy ($\Delta E)$. This gives rise to the observed uncertainty such that the product of these two attributes yields Heisenberg's Uncertainty. The 1/r propagation of gravitons in my later proposal resolves the issue of renormalization of gravity by providing a natural cut-off when ``r'' equals the Planck length. One implication of my proposal is gravity may not be ideally attractive, as spin-dependent nuclear force contains a tiny repulsive component. [Preview Abstract] |
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FR.00089: Information Download: Data Management Monitoring and Computing Analysis for STAR at PDSF Ariel Fleming, Doug Olson, Eric Hjort Data management and computing analysis for the Solenoidal Tracker at RHIC (STAR) is an essential effort to ensure efficient use of the limited computing resources. Trying to keep account of the usage of the Parallel Distributed Systems Facility (PDSF) computing facility and the number of files kept at the two different facilities, RHIC Computing Facility (RCF) and PDSF, becomes a very intensive job. The purpose of this research is to find a way to monitor the usage of the PDSF cluster and to keep account of the number of files each facility carries so that the datasets are the same. In analyzing the workload characteristics on PDSF (length of the batch jobs) over 3 years it was apparent that the most jobs were fairly long in the early years. As time progressed the jobs were shorter due to the fact that much of the activity was due to the analysis of the data. The software developed to count the files at RCF and PDSF has been an asset to researchers because now they have access to identifying the files that are needed at the facilities. This development prints the file monitoring results automatically to a web page making it easy to monitor the replication of files from RCF and PDSF. [Preview Abstract] |
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FR.00090: Isospin (N/Z) dependence of isotopic yield ratios as a function of fragment kinetic energy Carl Schreck, Sherry Yennello, Brian Stein, Sarah Soisson Assessing the effect of isospin (N/Z) on nuclear fragmentation is important in understanding the symmetry energy contribution to nuclear reactions. Previous studies have observed that the fragment excitation energy spectra for isotopes with~smaller isospin (more neutron deficient isotopes) are significantly more energetic. We present data which utilizes isobaric beams of N/Z$>$1 ($^{20}$F), N/Z=1 ($^{20}$Ne), and N/Z$<$1 ($^{20}$Na) to determine the effect of the beam isospin on projectile fragmentation. Beams were obtained at the MARS (Momentum Achromat Recoil Separator) facility at the Texas A{\&}M Cyclotron Institute with $^{20}$F+Au, $^{20}$Ne+Au, and $^{20}$Na+Au reactions at 32Mev/A. Fragments were then detected with the FAUST detector (Forward Array Using Silicon Technology), allowing for isotopic identification of charged particles to Z = 6, thus enabling complete reconstruction of the quasi-particle in both charge and mass for peripheral reactions in which there are small numbers of nucleons transferred. For each fragment produced in these reactions, center of mass fragment energy spectra are produced. These Isotopic energy spectra will be presented as a function of the isospin of the beam. [Preview Abstract] |
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FR.00091: Geometrical Isospin Daniel C. Galehouse A theory of motion based on geometrical mathematics similar to general relativity has been developed for interacting quantum particles. Curvilinear coordinate systems describe smooth interactions due to conformal transformations. Spin can be included, following the Dirac equation, and leads to a description of electrons and neutrinos that interconvert in eight dimensions by hyper-rotation. Particles may have a propagational mass that is detectably different from their rest mass. [Preview Abstract] |
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FR.00092: The 26Al(p,g)27Si Reaction at DRAGON Heather Crawford The 26Al(p,g)27Si reaction is important for nuclear astrophysics, as 26Al is directly observable in supernovae explosions due to its decay with a characteristic gamma. This allows comparison of observational data with models, the accuracy of which depends on how well known the reaction rates for the processes involved are. As the only direct destruction pathway for 26Al aside from its beta decay, the 26Al(p,g)27Si reaction is an integral part of the 26Al system, and an accurate measure of its rate, determined mainly by the strength of available resonance reactions, is critical. The strength of the 188 keV resonance is currently being directly studied for the first time in inverse kinematics, using the DRAGON facility at TRIUMF. A 26Al radioactive beam incident on a windowless H2 gas target gives rise to 27Si recoils, which are detected through the coincidence of a prompt gamma, and a heavy ion signal at the end detectors. Data is being analyzed to separate true events from background and determine the thick target yield. Also important is an analysis of beam intensity and composition, using data from DRAGON detectors and faraday cups. Results from these latter aspects of the study will be reported on. [Preview Abstract] |
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FR.00093: Analysis of Multi-dimensional Data from the YSU Miniball at the SPring-8 Synchrotron, Japan Ronald Propri In recent years, attempts at triggering energy release from long-lived nuclear isomers have been both a scientific and political focus. The study of 178Hfm2 has been of particular interest due to its attractive energetic properties. In light of the controversial nature of claims concerning positive experimental results, much attention was given to the analysis of data from different types of experiments. This poster will illustrate methods of analysis of multi-dimensional data recorded at SPring-8 with the YSU Miniball detector array, including timing characteristics, gamma-gamma coincidences, and the software package specially designed for the unique properties of our system. [Preview Abstract] |
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FR.00094: USB Control of Multiplexed Shaper Electronic for a Segmented Silicon Array M. Hodek, C.J. Metelko, R.T. deSouza, A. Alexander We report on an electronic system, MASE (Multiplexed Analog Shaped Electronics), designed to simplify the analog processing and readout from a highly segmented silicon detector array. This system focuses on providing good energy resolution and adequate timing information for up to 1024 channels. It consists of 16-channel boards which can be either used independently or as part of a larger system. The analog portion of each channel has low and high gain shapers with associated leading edge discriminators and peak hold circuits. The logic for readout of the analog signals is performed by two FPGA chips located on each board. Readout of MASE channels is multiplexed, an approach that works well for a broad range of experiments. To aid in the debugging and monitoring of an experiment, signals are also multiplexed for inspection purposes. The gain of each shaper and the threshold of each discriminator is adjustable through DACs. Shaper and discriminator control parameters are transferred through a USB port to an onboard FIFO chip. This chip transfers the commands to the FPGAs, which control the shaper/discriminator circuits and the acquisition sequence. A Tcl/Tk graphical user interface coupled to a C++ source code allows the user to easily provide the control parameters to the MASE electronics. [Preview Abstract] |
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FR.00095: The search for triggered decay of metastable isomers David Gohlke Some nuclear excited states can achieve astounding lifetimes, storing significant amounts of energy for long times. These metastable isomers are of great interest from a purely scientific perspective and have been suggested as potentially supporting various applications. The interaction of externally-produced radiation with isomeric nuclei may provide a means of inducing a release of the stored energy upon demand. This poster will discuss experimental planning for studies of energy-releasing reactions with real photons on $^{121m}$Sn and $^{166m}$Ho. [Preview Abstract] |
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FR.00096: Search for isomers in $^{64}$Ge Beverly Lau, Ani Aprahamian, Andreas Woehr, Timo Griesel, Plamen Boutachkov, Boris Skorodumov, Sergio Almaraz-Calderon, Matthew Quinn The $^{64}$Ge nucleus is produced from collisions of 36 MeV $^{12}$C beam on a $^{54}$Fe target at the Institute for Structure {\&} Nuclear Astrophysics (ISNAP) located at the University of Notre Dame. The beam was produced using a tandem Van de Graaff accelerator running a pelletron charging system. Scintillation counters and Germanium detectors were used to detect neutrons in coincidence with gamma rays for clear channel identification. Comparison to existing data may confirm the presence of $^{64}$Ge in the reaction products. Further analysis will be done to determine the existence of isomeric states in $^{64}$Ge. This nucleus is thought to be a ``waiting-point'' nucleus for the rapid proton capture process (rp-process). The identification of isomers will be used to study the impact of isomers on rp-process nucleosynthesis. There are existing theoretical calculations within the projected shell model that indicate the existence of an isomer in this nucleus at an excitation energy of 900 keV$^{ 1}$. Isomers were recently discussed in Physics Today$^{2}$. References: \begin{enumerate} \item Y. Sun. Phys. Rev. C 70 (2004) 051301(R) \item P. M. Walker and J. J. Carroll. Phys. Today. June 2005. \end{enumerate} [Preview Abstract] |
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FR.00097: Time and Position Calibration of IceCube Optical Modules William Robbins The IceCube high-energy neutrino telescope uses optical modules (OMs- each containing a photomultiplier tube) embedded in glacial ice to detect Cherenkov photons in order to reconstruct the path of neutrino-induced muons. To accurately reconstruct muon tracks, and thusly perform neutrino astronomy, the detector must be well calibrated to minimize uncertainties in the optical module (OM) positions and the arrival times of photons at each OM. In the process of constructing a kilometer-scale detector near the South Pole, the IceCube Collaboration recently deployed a string of sixty OMs deep in the Antarctic Ice and sixteen OMs at the surface above the string. Using down-going cosmic ray muons, it is possible to verify the IceCube time and position calibrations determined by other in situ methods. This work will describe a calibration technique used by IceCube and present results of recent experimental data from cosmic ray muons. [Preview Abstract] |
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FR.00098: In-flight Calibration of CREST Michael Strongman, James Musser The Cosmic Ray Electron Synchrotron Telescope (CREST) is a balloon-borne experiment that seeks to measure the cosmic ray electron spectrum. The spatial distribution of sources, such as supernova, is expected to cause a dramatic departure from the power law energy spectrum. CREST identifies electrons from the linear train of synchrotron radiation produced by the electrons motion in the Earth's magnetic field. A scaled prototype is scheduled to fly the summer of 2005 as a proof-of-concept flight. The details of the implementation of the pulser system, which allows for in-flight calibration of the photodetector array, will be shown. [Preview Abstract] |
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FR.00099: Tracking Single and Multiple Events in MoNA Andrew Stump, Andrew Ratkiewicz The Modular Neutron Array (MoNA) is a large area detector consisting of 144 plastic scintillating bars housed at the National Superconducting Cyclotron Laboratory (NSCL). Used in conjunction with a 4 T sweeper magnet, it is a high- efficiency neutron detector for studying nuclei near or past the neutron drip line. First experiments concentrated on the study of nuclei decaying by single neutron emission. However, future experiments are planned to explore for example the decay of $^{13}$Li into $^{11}$Li and two neutrons. Thus it will be necessary to distinguish one-neutron hits from two-neutron hits in MoNA. We used the data from the decay of $^{25}$O into $^{24}$O and a neutron as well as the decay of excited $^{11}$Be into $^{10}$Be and a neutron to characterize single neutron events. Subsequently we identified two-neutron events from the decay of excited $^{12}$Be into $^{10}$Be and two neutrons. [Preview Abstract] |
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FR.00100: Writing of a GEANT4 simulation of E906 at FNAL Main Injector Aldo Raeliarijaona Following Fermilab E866/NuSea, which determined the light antiquark asymmetry in the proton, as well as many other results, Fermilab E906 is an experiment that will measure nucleon and nuclear structure at the parton level using Drell-Yan scattering. With significant improvement on statistical errors above Bjorken x = 0.2, E906 will go further than the E866/NuSea could on measurements. In order to improve modeling for E906 a new GEANT4 simulation was created in a new code, instead of using the old simulation done in FORTRAN in GEANT3. We will report on new calculations to verify the optimal absorber arrangement in the first magnet of the E906 spectrometer. [Preview Abstract] |
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FR.00101: MoNA Calibration and Neutron Tracking Shea Mosby, Evan Mosby, Warren F. Rogers The Modular Neutron Array (MoNA) at the NSCL consists of 144 2-m long scintillator-bars stacked 16 high by 9 layers deep. The array, used in conjunction with a large sweeper magnet, is designed to investigate properties of neutron rich nuclei near the drip-line. In order to properly track neutrons resulting from breakup reactions, it is imperative that all bars be carefully calibrated for position. While different PMT response times can be measured and corrected for by applying precise offsets to the data, there remains no method for measuring and correcting for slight physical misalignment of the individual bars. We’ve developed a method which uses the straight-line paths created by cosmic muons passing through the array to ``tie'' all the bars together into one consistent position calibration. We’ve developed an algorithm which filters high-multiplicity muon events from the data stream and plots their individual tracks through the array. A least square fit is applied to each track and the resulting individual bar offsets from the fitted line are statistically compiled. This method can be extended to provide a tool for distinguishing multiple scatterings of individual neutrons from higher multiplicity neutron events, which will be important for future experiments. Results will be presented. Work supported by NSF grant \#PHY05-2010. [Preview Abstract] |
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FR.00102: Performance Evaluation of Neutron Polarimeter NPOL Shumpei Noji, Kenjiro Miki A high performance neutron polarimeter NPOL has been constructed for the measurement of polarization correlation function for the ($d$, $pn[{}^1 S _0]$) reaction for the test of EPR paradox in a system of unlike fermions. The NPOLsystem consists of 12 planes of two-dimensional position-sensitiveneutron detectors with a size of $60 \times 60 \times 3.0 \, \mathrm{cm}^3$. Neutron polarization is determined from the azimuthal distributionof the elastic $\vec{n} + p$ scattering in the scintillator. The effective analyzing power of NPOL have been calibrated by using the polarized neutrons from the ${}^6 \mathrm{Li}(\vec{d},\vec{n})\mathrm{X}$ reaction at $T _d = 270 \,\mathrm{MeV}$. We will report the effective analyzing power and the double scattering efficiency. [Preview Abstract] |
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FR.00103: Pion, kaon, proton and antiproton spectra in CuCu collisions at $\sqrt{s_{NN}}=200$ GeV at RHIC Jing Liu Collisions of untrarelativistic nuclei at RHIC provide a unique means to create nuclear matter of high energy density. Study of the various properties of this dense matter requires systematic measurements of identified particle spectra.The combination of STAR time of flight (TOF) based on MRPC (Multi-gap Resistive Plate Chamber) and Time Projection Chamber(TPC) detectors offers particle identification (PID) over a wide transverse momentum ($p_T$) range. In this talk, We will present the progress of an analysis of the identified hadron spectra in Cu+Cu collisions at RHIC using state-of-the-art prototype electronics and MRPC TOF. Physics implication will be discussed. [Preview Abstract] |
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FR.00104: Measurement of the lifetime of an gold isotope Kazuhiro Kurihara The lifetime of unstable isotopes is one of the most important observables in nuclear physics, because it corresponds to the decay constant, from which we can investigate wave functions of the initial and final states. This measurement was carried out to experimentally demonstrate the exponential decay law and to understand the concept of lifetime. First of all, a sheet of gold sample was irradiated by neutrons which were generated by stopping protons of 12 MeV in Tohoku University cyclotron RI center facility. Then $\gamma$ ray emitted from the sample were repeatedly measured by a NaI scintillation counter for 8 days, each measurement lasting for 400 seconds. A peak was observed at about 410 keV in the NaI pulse height spectrum. It was consistent with the 411.8 keV energy for the $\gamma$ ray ejected from the $^{198}$Hg, the daughter nucleus of $^{198}$Au after $\beta$ decay. The observed count of the 411 keV $\gamma$ ray was gradually decreased as time passed. The decreasing counts were fitted well by an exponential decay curve and the lifetime $\tau$ was determined to be 3.92 days. It is consistent with the lifetime of $^{198}$Au. Therefore the unstable nucleus was identified $^{198}$Au. [Preview Abstract] |
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