Bulletin of the American Physical Society
2005 72nd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 10–12, 2005; Gainesville, FL
Session ED: Nuclear Physics |
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Chair: Henry Weller, Duke University Room: Hilton Hickory |
Thursday, November 10, 2005 4:15PM - 4:27PM |
ED.00001: Measrement of Electron Impacat Excitation Cross Sections of n = 3-1 Transitions in Heliumlike Kr$^{34+}$ A.J. Smith, H. Chen, D. Thorn, P. Beiersdorfer We have measured the ratio of electron impact excitation cross sections for the intercombination line 1s3p $^{3}$P$_{1}$ - 1s$^ {2}$ $^{1}$S$_{0}$ and the resonance line 1s3p $^{1}$P$_{1}$ - 1s$^{2}$ $^{1}$S$_{0}$ in heliumlike Kr$^{34+}$ at relativistic electron beam energies. The lines are excited in the Lawrence Livermore National Laboratory's electron beam ion trap (EBIT-1) operated in the high energy mode, SuperEBIT. X-ray spectra were recorded using a high-resolution microcalorimeter. We present a comparison of the measured ratios and theoretical predictions of these ratios. This work was performed under the auspices of the U. S. Department of Energy by Morehouse College under contract No. DE-FG02-98ER14877 and by LLNL under contract No. W-7405-ENG- 48. We gratefully acknowledge support by the LLNL Research Collaborations Program for HBCU's. [Preview Abstract] |
Thursday, November 10, 2005 4:27PM - 4:39PM |
ED.00002: A One-Dimensional Dual-Radiator RICH Detector with Wavelength Shifter Readout -- Principle and Monte Carlo Simulations Naipy Perez, Brain Beckford, Alejandro de la Puente$^2$, Joerg Reinhold Ring imaging \v Cerenkov detectors (RICH) measure a particle's velocity by projecting the \v Cerenkov light cone on a plane and determining the radius of the resulting ring. Traditional detectors either employ a large number of photomultipliers (PMTs) or gaseous detectors with a highly segmented photosensitive cathode. Both principles require the readout of a large number of channels. For selected applications it may be sufficient, however, to measure a one-dimensional projection of the ring. This could be achieved with a plane of wavelength shifting bars that are read out by PMTs on both sides. This would result in a significantly reduced number of channels and therefore also more affordable designs. The talk will present the principle idea, Monte Carlo simulations of the performance of such a system based on the results from a beam test. [Preview Abstract] |
Thursday, November 10, 2005 4:39PM - 4:51PM |
ED.00003: Detection of Cherenkov Light with Wavelength Shifting Acrylic Plastic Brian Beckford, Naipy Perez, Alejandro de la Puente$^2$, Joerg Reinhold The collection efficiency for Cherenkov light from a fused silica radiator incident on a wavelength shifting acrylic plate (WLS) has been determined during a beam test at the proton synchrotron at the KEK facility. The yield of the photoelectrons produced through internally generated Cherenkov light as well as light incident from the radiator was measured as a function of the momentum of the incident beam. The yield is directly proportional to $\sin^2_\Theta$ where $\Theta$ is the angle of the Cherenkov light created. This allows the extraction of the photon collection efficiency of the WLS which is roughly 50.8\% for photons created in the fused silica radiator. This is comparable to more traditional means of detecting photons in RICH detectors, like CsI photocathodes or large PMT arrays. Currently, small prototype tests and Monte Carlo simulations are being conducted to investigate the feasibility of using arrays of WLS bars as a means of constructing cost efficient one-dimensional RICH detectors. [Preview Abstract] |
Thursday, November 10, 2005 4:51PM - 5:03PM |
ED.00004: Particle Identification for JLab Experiment E94-107 Armando Acha, P. Markowitz Experiment E94-107 at Jefferson Lab, Hall A took data on a waterfall target in June 2005. The particle identification for the experiment required separating kaons from large pion and proton backgrounds, and electrons from pion backgrounds. Particle identification (PID) of kaons, positive pions and protons in the left (hadron) High Resolution Spectrometer arm used two threshold aerogel Cerenkov detectors as well as a RICH detector. In the right (electron) arm a gas Cerenkov detector was used to distinguish electrons and negative pions. A lead glass preshower and shower detector was used to enhance the separation between electrons and negative pions. A timing coincidence between double layers of scintillators in each arm was used to identify kaons coincident with the electrons and reject background events.. Details of the detector configuration and its performance will be presented. [Preview Abstract] |
Thursday, November 10, 2005 5:03PM - 5:15PM |
ED.00005: Perturbative Calculation of Nucleon Compton Scattering Richard Thomson, Chueng Ji Perturbative calculations of proton Compton scattering are compared with recent experimental results from JLAB. Normalization of the results using the proton form factor suggest that experimental cross sections for real Compton scattering (RCS) are approaching our calculated results as CM energy, W, increases. A recent virtual Compton scattering (VCS) experiment suggests that, for large W, the cross section becomes independent of $Q^2 = -(4-$momentum of the virtual photon$)^2$. This hypothesis is considered in the light of our perturbative calculations for VCS. Finally, we explore a link between the perturbative approach to DVCS and the handbag diagram approach using GPDs. [Preview Abstract] |
Thursday, November 10, 2005 5:15PM - 5:27PM |
ED.00006: Half-life measurements of several states in $^{95,97}$Sr, $^{97,100,104}$Zr, $^{106}$Mo and $^{148,150}$Ce J.K. Hwang, A.V. Ramayya, J.H. Hamilton, Y.X. Luo, A.V. Daniel, G.M. Ter-Akopian, J.D. Cole, S.J. Zhu Half-lives (T$_{1/2}$) of several states in $^{95,97}$Sr, $^{97,100,104}$Zr, $^{106}$Mo and $^{148,150} $Ce which decay by delayed $\gamma$ transitions, were determined from time-gated triple $\gamma$ coincidence method. Transition energy dependent effects such as time-walks, time-jitters, amplitude-walks and possible timing fluctuation of Ge detectors that contribute to the width of time window are taken into consideration. It is shown that the normalized triple $\gamma$ coincidence counts (the inverse of N1) of two prompt cascades with the similar transition energies are similar. Also, it is observed that the real triple $\gamma$ coincidence counts in the prompt cascades change systematically along with the change of the coincidence time-window and three transition energies. The half-lives of the states in the delayed cascades are determined by using the prompt cascades with the similar transition energies as delayed cascades. The half-life of 2$^+$ state in $^{104}$Zr is measured to be 1.9(2) nsec. The obtained B(E2$;$0$^+ \rightarrow 2^+$)(e$^2$b$^2$) value and quadrupole deformation ($\beta_2$) are 2.0(2) (e$^2$b$^2$) and 0.47(5). It is reported that, except $^{102}$Sr, $^{104}$Zr($\beta_2$=0.47(5)) has the most deformed 2$^+$ state among medium and heavy even-even nuclei. [Preview Abstract] |
Thursday, November 10, 2005 5:27PM - 5:39PM |
ED.00007: High Resolution 1p Shell Hypernuclear Spectroscopy at JLAB Pete Markowitz Hypernuclear physics is a unique tool for providing information on the nature of the potential between nucleons and strange baryons. Information on the nature of the force between nucleons and strange baryons, i.e. the Lambda-N interaction, can be accessed by studying the spectroscopy of nuclei in which a nucleon has been replaced by a Lambda particle to form a bound state. The experiment E94107 at Jefferson Lab, Hall A, using a pair of high resolution spectrometers coupled to a pair of septum magnets, together with a RICH detector for particle identification, completed its first measurements of hypernuclear electroproduction on carbon and beryllium targets in June 2004. Data on oxygen using a windowless waterfall target were recently taken during June 2005. Results on Carbon and Beryllium and preliminary data on oxygen will be presented and compared with theoretical models [Preview Abstract] |
Thursday, November 10, 2005 5:39PM - 5:51PM |
ED.00008: $0_{^+} $ states of the $^{12}$C nucleus: Faddeev calculation in configurations space Branislav Vlahovic, Igor Filikhin, Vladimir Suslov The $\alpha $-cluster model and Faddeev equations in configuration space are applied to study the $^{12}$C nucleus. The model includes the Ali-Bodmer nuclear potential [1], attractive three-body potential, and takes into account the Coulomb interaction. An s-wave model [2] is adapted and parameters of the three-body potential are chosen to describe the first two 0$_{^+} $ levels of $^{12}$C. The value of the range parameter of the potential is adjusted to reproduce the position of diffraction minimum for the elastic form factor of $^{12}$C. The model assumes a strong distortion of the charge density of $\alpha $ clusters inside the $^{12}$C nucleus. It was found that the most probable configuration of the $\alpha $-clusters in the 0$_1^+$ state corresponds to an equilateral triangle with sides as large as 3.5 fm and in the 0$_2^+ $ state to a linear chain with the values of 2.9 fm and 13.1 fm for each link. Having calculated low-lying levels of $^{12}$C, we found that the contributions of higher partial waves of nuclear interaction to the energy of 3$\alpha $-system are unnaturally large and some states turn to be overbound. Upon applying the method [3] based on the Pade approximants we've got a satisfactory description the 0$_3^+ $ and 0$_4^+ $ states [4]. Additional $0^+$ broad resonance obtained in [3] was not found. 1. S. Ali, A. R. Bodmer, Nucl. Phys. 80, 99 (1966). 2. Z. Papp, et al. Few-Body Systems 30, 31 (2001). 3. C. Kurokawa and K. Kato, Phys. Rev. C76, 021301-1 (2005). 4. http://www.tunl.duke.edu/nucldata/. [Preview Abstract] |
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