Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session Q1: Neutrinos I
Sponsoring Units: DAP DPFChair: George Fuller, University of California, San Diego
Room: Hyatt Regency Dallas Landmark A
Monday, April 24, 2006 1:30PM - 2:06PM |
Q1.00001: Cosmic Microwave Background and Large Scale Structure Measures of Neutrino Mass Invited Speaker: The clustering of matter on the largest, cosmological scales has provided a window on the mass of the particle with the smallest cross-section, the neutrino. This results from the effects of the expected background of relic cosmological neutrinos on clustering from the largest to smallest scales in the linear theory of cosmological structure growth in combination with precision measures of cosmological matter clustering from observations of the cosmic microwave background and from galaxy surveys. I will review the theoretical underpinnings and caveats of the inferred neutrino mass limits from cosmological large scale structure and the status of current observations from the Wilkinson Microwave Anisotropy Probe of the the cosmic microwave background as well as the large scale structure measures from the Sloan Digital Sky Survey. In addition, I will highlight future cosmological probes of neutrino properties. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q1.00002: Neutrinos and Neutrino Physics: Still Center Stage in Core Collapse Supernovae Invited Speaker: Ascertaining the core collapse supernova mechanism and understanding all of the phenomena associated with such stellar explosions, such as their element synthesis and gravitational wave signatures, neutron star kicks, the spin of pulsars at birth, etc., will require three-dimensional precision models that include realistic neutrino transport, stellar core fluid instabilities, rotation, magnetic fields, a realistic stellar core equation of state for both sub- and super-nuclear densities, and realistic weak interactions. Only in the last decade has supernova modeling broken free from the confines of spherical symmetry. I will review the current state of the art. Even the most fundamental questions remain: How do core collapse supernovae explode? What role do the neutrinos play? While a recent emphasis has been placed on the role of magnetic fields in generating core collapse supernova explosions, the neutrinos still occupy center stage. Moreover, in light of the now experimentally determined fact that neutrinos have mass, neutrino transport in core collapse supernovae takes on a whole new complexity. Previously, neutrino transport was well described by Boltzmann kinetic theory, but now more faithful modeling will require quantum kinetics. The role of neutrino mixing in the core collapse supernova mechanism remains virtually unexplored, with the potential for significant surprises. It is, as I will discuss, one of the frontiers in core collapse supernova theory. Finally, the development of precision three-dimensional supernova models will provide yet another scientific opportunity beyond the chance to ascertain how stars die and produce the elements necessary for life. Together with detailed observations, especially of the neutrino and gravitational wave emissions in the event of a Galactic supernova, detailed supernova models will allow us to use core collapse supernovae as laboratories for fundamental physics. I will discuss some of the possibilities. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q1.00003: The Neutrino World Invited Speaker: The discovery of neutrino mass has raised very interesting questions about the neutrinos and their connections to the rest of physics and astrophysics. We will discuss these questions and the ideas for answering them through future experiments. Ultimately, one would like to discover the origin of neutrino mass. We will discuss some speculations on this origin. [Preview Abstract] |
Session Q2: Implications of QCD Phase Transitions
Sponsoring Units: DNPChair: Vickie Green, Vanderbilt University
Room: Hyatt Regency Dallas Landmark B
Monday, April 24, 2006 1:30PM - 2:06PM |
Q2.00001: TBD Invited Speaker: |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q2.00002: Hitchhiker's Guide to the Early Universe Invited Speaker: The new standard picture of the early, expanding and accelerating Universe is reviewed at an accessible level. The Hubble expansion, the Robertson-Walker metric, and the cosmological constant are discussed. Special emphasis is placed on the thermal history of the early Universe, with the goal of appreciating the relevance of the QCD phase transition. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q2.00003: Probing the Properties of the Big Bang Quark Matter Invited Speaker: The combination of experiments at the Relativistic Heavy Ion Collider and calculations of QCD thermodynamics done using the methods of lattice gauge theory are revealing the properties of the matter that filled the universe in the microseconds after the big bang. I will present a look at what we have learned recently, and what we may hope to learn soon. Given that the former includes surprises--who could have guessed that the first property of the quark-gluon plasma we would learn about from RHIC would be its shear viscosity, leave apart that the quark-gluon plasma would prove to be such an ideal liquid? The latter comes with no guarantees. Along the way, I will mention an insight that has come from calculations done using AdS/CFT dualities first developed by string theorists. [Preview Abstract] |
Session Q3: Particle Acceleration
Sponsoring Units: DAP DPPChair: James Drake, University of Maryland
Room: Hyatt Regency Dallas Landmark C
Monday, April 24, 2006 1:30PM - 2:06PM |
Q3.00001: Observing Particle Acceleration with RHESSI Invited Speaker: The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) was designed to study particle acceleration in solar flares by imaging spectroscopy of both bremsstrahlung from electrons and nuclear lines from ion interactions. I will review several of the major results of these studies since the launch of RHESSI in February 2002. RHESSI's x-ray and gamma-ray detectors are also being used to study electrons accelerated to high energies in other sites, such as the Crab nebula and thunderclouds on Earth; I will review the status of these observations as well. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q3.00002: Current Status of Shock Acceleration Theory Invited Speaker: The main features of nonlinear diffusive shock acceleration are now reasonably well understood after several decades of work by many individuals. Several distinct approaches have converged to give a reasonably consistent picture of the process. These will be briefly described. The interesting new development in the last few years is the increasing attention being paid to mesoscopic instabilities and their potential importance for magnetic field amplification, This may well be the last missing piece of the jig-saw, but raises serious technical problems for the theoretical study of the acceleration process as well as some fascinating physics issues. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q3.00003: The Importance of magnetic-field angle in diffusive shock acceleration of cosmic rays Invited Speaker: We discuss the physics of charged-particle acceleration by shock waves, focussing on the importance of the shock-normal angle. This has important applications for our understanding of supernovae shocks, the solar-wind termination shock, and propagating shocks near the Sun. For the case in which the shock normal is parallel to the incident field - a parallel shock - acceleration of particles to very high energies (e.g. the knee in the cosmic-ray spectrum, or $>$GeV energy solar cosmic rays) requires very special conditions to explain the observations. These include a strong increase in the magnetic field, perhaps due to excitation from the streaming cosmic rays. In this talk, we show that no such special circumstances are required when one considers acceleration at nearly perpendicular shocks. We suggest that the observations of high-energy charged particles can be accounted for using reasonable values for the diffusion coefficients and observed shock speeds. A critical issue in the theory of diffusive shock acceleration at nearly perpendicular shocks is the well-known injection problem. We suggest that, in actuality, there is no such injection problem and, in fact, the acceleration efficiency does not depend strongly on the shock-normal angle. This can be understood in terms of the increased cross-field transport arising from so-called field-line random walk due to the large-scale (ccompared to the particle gyroradii) turbulent magnetic field. [Preview Abstract] |
Session Q4: Three-Body Systems
Sponsoring Units: GFBChair: Werner Tornow, Duke University
Room: Hyatt Regency Dallas Marsalis A
Monday, April 24, 2006 1:30PM - 2:06PM |
Q4.00001: Two-Body Photodisintegration of ${^3\rm{He}}$ between 0.4 and 1.5 GeV Invited Speaker: The $\gamma {^3\rm{He}}\rightarrow pd$ reaction was measured with the CLAS detector at Jefferson Lab for photon energies between 0.4 and 1.5 GeV and proton CM angles $\theta^p_{CM}$ between 40$^\circ$ and 140$^\circ$. It is complementary to the three-body breakup of $^3$He with respect to studying three-body mechanisms. At all photon energies for our experiment, the differential cross sections exhibit a very strong forward-to-backward asymmetry --- approximately one order of magnitude. An interesting feature of the differential cross sections is that their slope does not depend on the photon energy and there is a change of slope at $\theta^p_{CM}=120^\circ$ seen at all photon energies. The invariant cross sections fall off with $s$ (where $s$ is the total CM energy) much faster than expected by the quark counting rules $[1]$. The latter predict that in the asymptotic regime $t\rightarrow\infty$ the invariant cross sections should scale as $s^{-17}$, whereas our data scale as $s^{-22}$. A comparison of our preliminary results with the cross sections predicted by Jean-Marc Laget's model $[2]$ shows that the differential cross sections for angles greater than 60$^\circ$ are sensitive to contributions from three-body mechanisms. The relative importance of the latter, with respect to one- and two-body mechanisms, is larger at 0.6 - 0.8 GeV than at higher energies. This has already been observed in our data for $\gamma {^3\rm{He}}\rightarrow ppn$ $[3]$ and seems to be a characteristic of the three-body mechanisms at medium energies. \vspace{6mm} \newline 1. S.J.~Brodsky and G.R.~Farrar, Phys. Rev. Lett. \textbf{31}, 1153 (1973) \\ 2. J-M.~Laget, Phys. Rev. C \textbf{38}, 2993 (1988)\\ 3. S.~Niccolai \textit{et al.}, Phys. Rev. C \textbf{70}, 064003 (2004) [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q4.00002: Probing Short Range Nuclear Properties in Photodisintegration of Few-Nucleon Systems Invited Speaker: High momentum transfer photodisintegration reactions involving few-nucleon systems represent a powerful tools for studying the nuclear dynamics at short space-time separations. We review on several aspects of this research, such us understanding the nature of short range three nucleon correlations, studying the mechanism of three-nucleon forces and probing the dynamics of quark-hadron transition in the nuclear medium. Particular processes we review are the high $Q^2$ three-body break up reactions, $90^0$ center of mass photodisintegration of $pp$ and $pn$ pairs in the $^3He$ as well as production of energetic deuterons in the current fragmentation region of the reaction. We demonstrate how these studies could allow us to extract unique information about properties of strong interaction which are inaccessible in studies of nucleon-nucleon scattering. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q4.00003: Three-nucleon forces: new developments Invited Speaker: It is well known from microscopic few- and many-body studies that three-nucleon forces are important for quantitative understanding of various phenomena in nuclear physics. Three-nucleon forces that cannot be reduced to pair-wise nucleon-nucleon interactions arise naturally in the context of meson-exchange theory and at the more fundamental level of QCD. Chiral effective field theory provides a powerful and promising approach to determine two-, three- and more-nucleon forces in a systematic way based on the approximate and spontaneously broken chiral symmetry of QCD. Recent developments along these lines will be discussed. Future directions in this field will be outlined. [Preview Abstract] |
Session Q5: Evolution: From the Big Bang to Us
Sponsoring Units: FPS FEdChair: Barbara Levi, Physics Today
Room: Hyatt Regency Dallas Pegasus B
Monday, April 24, 2006 1:30PM - 2:06PM |
Q5.00001: Evolution of the Universe Invited Speaker: Cosmology is in the midst of a scientific revolution that is establishing its lasting foundations. The good agreement between many different sorts of observations and the predictions of the now-standard Lambda Cold Dark Matter (LCDM) theory gives us hope that this is humanity's first picture of the history of the universe as a whole that might actually be true. An unexpected feature of this new picture is that we humans appear to be central or special in many ways -- for example, we are made of the rarest stuff in the universe (stardust); we are intermediate in size between the smallest possible size (the Planck length) and the largest size (the cosmic horizon); and we are living at a pivotal time: the period in the history of the universe when its expansion began to accelerate rather than slow down, and in the middle of the ten-billion-year lifetime of our solar system and of the billion year most habitable period of our planet, and at what must be the end of the exponential growth of human impact on the earth. This talk\footnote{Based on a new book, The View from the Center of the Universe: Discovering Our Extraordinary Place in the Cosmos, by Joel R. Primack and Nancy Ellen Abrams (Riverhead Books, April 2006).} will review key observations that support modern cosmology, describe some symbolic ways of understanding the modern cosmos, and discuss some possible implications of a cosmic perspective for our 21st century worldview. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q5.00002: Evolution of a Habitable Planet Invited Speaker: Earth has remained habitable, and inhabited, over most of its 4.5-Gyr history despite an appreciable (30{\%}) increase in solar luminosity over time and despite catastrophic events such as asteroid impacts and ``Snowball Earth'' episodes that have threatened biological survival on a global scale. Life has survived partly because of the resilience of the biota and partly because of feedback mechanisms that help to stabilize Earth's global climate. In particular, buildup of volcanic CO$_{2}$ during times when the climate is cold provides a strong negative feedback that helps keep Earth within the temperature regime favorable to life. The same processes that help stabilize Earth's climate should operate on other Earth-like planets, if they exist; thus, it is plausible that life could exist elsewhere. This hypothesis is now on the verge of being tested. NASA's twin \textit{Terrestrial Planet Finder (TPF)} missions, which could be launched as early as 2015-2020, will look for Earth-like planets around nearby stars and, if they are found, provide spectroscopic information on their atmospheres. Between them, these missions should be able to look for absorption bands of O$_{2}$, H$_{2}$O, CO$_{2}$, and O$_{3}$. Both O$_{2}$ and O$_{3}$ are considered to be good indicators of life for planets orbiting within the liquid water habitable zone of their parent star. NASA should be encouraged to give these missions high priority, so that we can answer these fundamental questions about the distribution of life in the universe. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q5.00003: Evolution of Biological Diversity Invited Speaker: A conservative estimate posits approximately ten million species presently inhabiting Earth, and these are clearly only a small fraction of those that have existed throughout Earth's history. Although various types of selective mechanisms have been identified as generating this diversity, and several chance mechanisms as well, the relative importance of these mechanisms is not firmly resolved. We review the current status of the discussion and some of the associated political and social ramifications. [Preview Abstract] |
Session Q6: Advanced Acceleration Techniques for Future Energy Frontier Accelerators
Sponsoring Units: DPBChair: James Rosenzweig, University of California, Los Angeles
Room: Hyatt Regency Dallas Cumberland J
Monday, April 24, 2006 1:30PM - 2:06PM |
Q6.00001: A Plasma Afterburner for the ILC Invited Speaker: |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q6.00002: Prospects for a TeV Laser Wakefield Accelerator Invited Speaker: |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q6.00003: Ultra-strong plasma lenses for final focus and other applications Invited Speaker: |
Session Q8: Electromagnetic Interactions
Sponsoring Units: DNPChair: Ioana Niculescu, James Madison University
Room: Hyatt Regency Dallas Cumberland A
Monday, April 24, 2006 1:30PM - 1:42PM |
Q8.00001: K*$^{0}$ photoproduction off the proton at CLAS Ishaq Hleiqawi, Ken Hicks The photoproduction of vector mesons has previously focused on the nonstrange sector, with $\rho $, $\omega $ or $\phi $ mesons in the final state. The lightest vector meson with nonzero strangeness is the K* of which little is known for photoproduction. The large acceptance of the CLAS detector makes it possible to capture both K* decay products, the pion and the kaon. In this talk we will show differential cross sections for the K*$^{0}\Sigma ^{+}$ final state over photon energies ranging from about 1.8 to 3.0 GeV. These data are compared with a theoretical model by Zhao \textit{et al.} using a quark-model for the K*-baryon couplings. Our data show that the forward-angle data are well described by the t-channel, hence providing constraints for the K*$\Sigma $N coupling constant At larger angles, the s-channel is well described by the model of Zhao \textit{et al.} over a range of angles and photon energies. The K* couplings determined from our data will more tightly constrain calculations for scalar kaon production, where K* exchange occurs as a virtual particle in the t-channel. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q8.00002: The Neutron Charge Form Factor at Low Q$^{2}$ Eugene Geis, Ricardo Alarcon, Michael Kohl, Richard Milner, Vitaly Ziskin At the MIT-Bates Linear Accelerator Center, the neutron charge form factor G$_{E}^{n}$ has been measured by means of (e,e'n) quasielastic scattering of polarized electrons from vector-polarized deuterium. The experiment used the longitudinally polarized stored electron beam of the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic deuterium target provided by an atomic beam source. The measurements have been carried out with the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST) with enhanced neutron detection capability. From the beam-target double polarization asymmetry with the target spin oriented perpendicular to the momentum transfer the form factor G$_{E}^{n}$ is extracted over a range of four-momentum transfer Q$^{2}$ between 0.12 and 0.60 (GeV/c)$^{2}$ with minimized systematic dependencies. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q8.00003: Inclusive Electron-Nucleus Scattering at $x>1$ and High $Q^2$ Donal Day Inclusive electron scattering from nuclei provides a rich, yet complicated mixture of physics that has yet to be fully exploited. The cross section at high momentum transfer arises from several reactions including quasi--elastic scattering from nucleons and deep inelastic scattering from the quark consitituents of the nucleons. Inclusive electron scattering presents the opportunity to investigate the transition from a regime where nucleon degrees of freedom hold sway to one where the more fundamental QCD interactions, involving quarks and gluons, are expected to dominate. Data at large values of $x$ over a range of $Q^2$ can be employed to study a wide variety of topics: nuclear momentum distributions, medium modifications of nucleon properties, the influence of final state interactions and the approach to $y$-scaling, the strength of nucleon-nucleon correlations at large $x$, and the approach to $x$- scaling. We recently completed such an experiment in Jefferson Lab's Hall C in which \mbox{6 GeV} electrons were scattered from both few-body nuclei and heavy nuclei at high momentum transfers. This experiment significantly extended the kinematic region at high momentum transfer and large (negative) $y$ (corresponding to large Bjorken $x$), explored in previous experiments. After a brief statement of the physics motivation for this experiment, we will present preliminary results. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q8.00004: CLAS g10 Analysis on Single Photopion Productions from Deuterium Wei Chen Photopion productions from nucleons are essential probes of the transition from meson-nucleon degrees of freedom to quark-gluon degrees of freedom in exclusive processes. The cross sections of these processes are also advantageous, for the investigation of the oscillatory behavior around the quark counting prediction, since they decrease relatively slower with energy compared with other photon-induced processes. Recent data from JLab experiment E94-104~[1,2] show dramatic change in the scaled differential cross-section from the $\gamma n \rightarrow \pi^- p$ and $\gamma p \rightarrow \pi^+ n$ processes in the center of mass energy between 1.8 GeV to about 2.4 GeV. We are carrying out a CLAS approved analysis~[3] of the JLab CLAS g10 data on the $\gamma n \rightarrow \pi^{-} p$ to investigate this dramatic behavior in much finer photon energy bins. Furthermore, the angular dependence of the scaling behavior for this process will also be studied in detail. We will report the status of the analysis in this presentation. \newline \newline References: \newline [1] L.Y. Zhu {\it et al.}, Phys. Rev. Lett. {\bf 91}, 022003 (2003).\newline [2] L.Y. Zhu {\it et al.}, Phys. Rev. C {\bf 71}, 044603 (2005); nucl-ex/0409018.\newline [3] http://www.tunl.duke.edu/$\sim$mep/clas/caa\_pion.pdf [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q8.00005: Search for the Onset of Color Transparency : JLab E02-110 experiment Lamiaa El Fassi The JLab E02-110 experiment was carried out in 2003-2004 using the CEBAF Large Acceptence Spectrometer (CLAS) located in Hall B at Jefferson Laboratory. The main goal of this experiment is to look for the onset of Color Transparency (CT) in the exclusive incoherent $\rho^{0}$ electroproduction on deuterium, carbon and iron. These measurements study the $Q^{2}$ dependence of the nuclear transparency $T_{A}$, the ratio of the nuclear per-nucleon ($\sigma _{A}/A$) to the free nucleon ($\sigma _{N}$) cross sections, at fixed coherence length $l_{c}$ of quark-antiquark fluctuations of the virtual photon. A significant increase of $T_{A}$ with $Q^{2}$ would be a signature of CT. A brief description to the experiment and the ongoing analysis work will be presented in this talk. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q8.00006: Precise Measurement of the Nuclear Dependence of the EMC Effect Aji Daniel Since the original observation of the modification of nuclear structure functions by the European Muon Collaboration, there has been intense experimental and theoretical efforts aimed at understanding nuclear effects in parton distribution functions. However, the experimental focus has been mainly on heavy nuclei. I will present preliminary results from Jefferson Lab experiment E03-103, a high precision measurement of the EMC effect with emphasis on the large $x_{Bj}$ region and few-body nuclei. Data on light nuclei ,$^3$He and $^4$He, will allow direct comparison to ``exact'', few-body calculations of the EMC effect and will allow an unambiguous determination of the functional form of the $A$- dependence of the EMC effect. The large $x_{Bj}$ data are particularly sensitive to conventional nuclear physics effects such as binding and Fermi motion and will constrain models that incorporates these effects. This, in turn, will provide information on the role of these conventional nuclear physics effects at lower $x_{Bj}$ where, more exotic effects are thought to be important. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q8.00007: Double and target asymmetries for the $e p \rightarrow e' p \pi^0$ production Angela Biselli An extensive experimental program to measure the spin structure of the nucleons is carried out in Hall B with the CLAS detector at Jefferson Lab using a polarized electron beam incident on a polarized target. Spin degrees of freedom offer the possibility to test, in an independent way, existing models of resonance electroproduction. The present analysis selects the exclusive channel $\vec{p}(\vec{e},e',p)\pi^{0}$ from data taken in 2000-2001, to extract single and double asymmetries in a $Q^2$ range from 0.2 to 0.75 $\rm{GeV}^2$ and a $W$ range from 1.1 to 1.6 GeV. Results of the asymmetries will be presented as a function of the center of mass decay angles of the $\pi^0$ and compared with the unitary isobar model MAID [1], the dynamic model by Sato and Lee [2] and the dynamic model DMT [3]. \newline \newline [1] D. Drechsel et al., Nucl. Phys. {\bf A}645 (1999) 145-174 \newline [2] H. Lee, Nucl. Phys. {\bf A}513 (1990) 511 \newline [3] S.~S. Kamalov, Phys. Lett. {\bf B} 522 (2001) 522 [Preview Abstract] |
Monday, April 24, 2006 2:54PM - 3:06PM |
Q8.00008: Exploration of Short Range Nucleon-Nucleon Correlations at JLab Douglas Higinbotham Measuring the probability of a nucleon-nucleon short range correlation inside a nucleus has historically been problematic. Competing mechanisms, such as final state re-scattering and meson exchange currents, can produce the same final state as one would expect from an initially correlated pair. Preliminary results of recent Jefferson Lab measurements, performed at kinematics which minimize the effects of such competing mechanisms, will be presented along with a quantitative picture of clustering in the nucleus. [Preview Abstract] |
Monday, April 24, 2006 3:06PM - 3:18PM |
Q8.00009: Study of the Exclusive d(e,e$^\prime$p)n Reaction Mechanism at High Q$^2$ Natalia Dashyan, Kim Egiyan High Q$^2$ d(e,e$^\prime$p)n scattering is one of the simplest and best ways to investigate the short range properties of the deuterium wave function (WF), possible modifications of the bound nucleon structure, as well as of the structure and nature of short range nucleon correlations (SRC). For these investigation, the mechanisms of this reaction should be understood properly. Although the d(e,e$^\prime$p)n reaction is the simplest one, its mechanism remains to be checked at high Q$^2$: short distances are involved and, therefore, it is unclear what degrees of freedom (nucleonic or quark-gluonic) play a more important role in electron-nucleon interaction. There are also subtle interplays between the interaction of different intermediate exited states of the struck fast nucleon with the second nucleon. To solve these problems the reaction should be investigated as completely as possible, at different kinematic conditions. We investigated the d(e,e$^\prime$p)n reaction mechanism in the Q$^2$ = (2 - 6) GeV$^2$ interval using the CLAS detector at Jefferson Lab. The angular and momentum distributions of recoil neutrons were studied in detail at momenta of p$_n $ = (0 - 2) GeV/c and in angular (relative to the transfered momentum direction) range 20$^o$ - 160$^o$. The experimental data are compared with the theoretical calculations [1] based on the diagrammatic approach of , and reasonable agreement was obtained at least in the momentum range p$_n \leq$ 1 GeV/c. [1]J.-M. Laget, Phys. Lett. {\bf B609}, 49 (2005). [Preview Abstract] |
Session Q9: Nuclear Structure
Sponsoring Units: DNPChair: Carlos Bertulani, University of Arizona
Room: Hyatt Regency Dallas Cumberland B
Monday, April 24, 2006 1:30PM - 1:42PM |
Q9.00001: The correlation of nucleon masses to nuclear stability is investigated E. Pamfiloff The decay chains and series of unstable isotopes and radioisotopes are studied with particular detailed analysis of nuclei masses and the change in mass experienced by individual nucleons of parent, daughter and product isotopes or other emissions. The data shows a direct correlation between the nucleon mass of a stable product nucleus and that of an unstable parent or daughter nucleon during the transition. This suggests that in addition to proton and neutron quantities, nuclear stability is dependent upon specific mass benchmarks for the nucleons of stable nuclei. It also indicates the probability that 238U is the parent of a series of stable and unstable isotopes situated below the Pb threshold with an unambiguous connection to stable 56Fe nucleons. To confirm these conclusions, the natural and artificial alpha emitter isotopes were also evaluated by the meticulous analysis of nucleon masses relative to the 1H proton. The developed database and system of evaluation allow those decay chain products of uncertain origin to be traced from unstable or stable nuclei back to the immediate source isotope in the series and then to the most probable origin. Often, more than one possible transition source isotope is identified. The system provided good results when tested against the incident and product particles of high and low energy interactions, including events of nuclear transmutation. Every transition from the initial nuclide to the final stable daughter or product demonstrates a strong correlation with a specific mass benchmark per nucleon as a third condition of nuclear stability. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q9.00002: Moments Method for the Nuclear Density of States Edgar Teran, Calvin Johnson We utilize statistical spectroscopy to model the nuclear level density in the interacting shell model. Low-lying statistical moments of each configuration of the shell model space are computed. Partial (configuration) densities are generated from the moments, and the sum of all the contributions is the total level density. Modified Breit-Wigner (MBW) distributions are used to model the partial densities. The properties of such functions allow for exact reproduction of the moments at large asymmetries, which are needed to accurately reproduce the overall level density. We work in the sd-shell with USD interaction, and the pf-shell with GXPF1, FPD6G an KB3G interactions. Results from level densities generated with method will be shown in the sd-shell and pf-shell, as well as comparisons to exact calculations and experimental data. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q9.00003: Level density of $^{60}$Ni from $^{59}$Co(d,n) and $^{58}$Fe($^{3}$He,n) reactions. A.V. Voinov, S.M. Grimes, S.I. Al-Quraishi, C.R. Brune, M.H. Hadizadeh, M.J. Hornish, T.N. Massey, J. O'Donnell, A. Salas The level density of $^{60}$Ni in the region below the particle separation energy has been obtained from neutron evaporation spectra measured in the $^{59}$Co(d,n) and $^{58}$Fe($^{3}$He,n) reactions at the Edwards Accelerator Laboratory at Ohio University. The main limitation of such a technique is an unknown distortion of the neutron spectra due to direct and pre-equilibrium reaction mechanisms. The purpose of this experiment was to measure the level density of $^{60}$Ni and estimate the contribution of the direct reaction mechanism, which is expected to be different for different incoming particles. The energy spectra and angular distribution of neutrons have been measured from both reactions. Both angular distributions exhibit a forward peaking shape due to the contribution from direct reaction mechanism The level density function has been extracted from neutron spectra taken from backward angles. The good statistics in the region of known discrete levels of residual $^{60}$Ni allowed one the absolute normalization of the obtained level density function. The level densities of $^{60}$Ni obtained from both reactions agree well, which indicates that the compound reaction is the major contribution to the differential reaction cross sections taken from backward angles. The Fermi-gas level density parameters have been obtained and compared to systematics. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q9.00004: High-spin states in $^{83}$Se N. Fotiades, A.F. Lisetskiy, J.A. Cizewski, R. Kr\"{u}cken, R.M. Clark, P. Fallon, I.Y. Lee, A.O. Macchiavelli, J.A. Becker, W. Younes High-spin states in $^{83}$Se have been studied following the fission of the $^{226}$Th compound nucleus formed in a fusion-evaporation reaction ($^{18}$O at 91~MeV on $^{208}$Pb). The Gammasphere array was used to detect $\gamma$-ray coincidences. This is the first observation of high-spin states above the 9/2$^{+}$ ground state of this nucleus and extends the level scheme up to spin (17/2$^{+}$). The coupling of the neutron hole in the $g_{9/2}$ orbital, which forms the ground state of $^{83}$Se, to the 2$^{+}$ and 4$^{+}$ yrast states in the $^{84}$Se core can account for the first four high-spin states in $^{83}$Se. There is generally good agreement between the experimentally observed high-spin states and predictions of shell-model calculations. This work has been supported in part by the U.S. Department of Energy under Contracts No. W-7405-ENG-36 (LANL), AC03-76SF00098 (LBNL) and W-7405-ENG-48 (LLNL) and by the National Science Foundation (Rutgers). [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q9.00005: Internal Conversion Coefficient Measurements of Transitions in $\mathrm{^{167}Lu}$ G. G\"urdal, C.W. Beausang, D.S. Brenner, H. Ai, R.F. Casten, A. Heinz, E. Williams, B. Crider, R. Raabe, D.J. Hartley, M. Carpenter, R.V.F. Janssens, T. Lauritsen, C.J. Lister, D. Seweryniak, S. Zhu, A.A. Hecht, J.X. Saladin Experimental internal conversion coefficients can be used to determine the multipolarities of electromagnetic transitions between nuclear energy levels and thus are valuable for assigning or confirming spins and parities of excited states. The normal and highly deformed bands of $\mathrm{^{167}Lu}$ were populated by the $\mathrm{^{123}Sb}(\mathrm{^{48}Ca}$,4n) reaction. Five fold $\gamma$ or $\gamma$-$\gamma$-e coincidence measurements were performed using Gammasphere and ICE Ball arrays at ANL. Internal conversion coefficients were determined for transitions in $\mathrm{^{167}Lu}$ and multipolarities were deduced. The preliminary results of the analysis will be presented. This work was supported by the U.S.D.O.E grants DE-FG02-88ER40417, DE-FG02-91ER-40609, DE-FG-05NA25929, DE-FG02-05ER41379, by the NSF grant number PHY-0300673 and in part by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q9.00006: Further tests of internal-conversion theory with precise $\gamma $- and x-ray spectroscopy. N. Nica, W.E. Rockwell, J.C. Hardy, V.E. Iacob, H.I. Park, J. Goodwin, M.B. Trzhaskovskaya Recently we reported [1] a measurement of the $K$-shell internal conversion coefficient (ICC) of the 80.2-keV $M4$ transition in $^{193}$Ir$^{m}$. Our result, $\alpha _{K}$=103.0(8), agreed well with the value 103.5(1) calculated with the $K$-shell hole accounted for in the ``frozen orbital'' approximation, and disagreed strongly with the value 92.2(1) calculated when the hole is ignored, a common approach taken in the past. Of the 100 transitions listed and compared with theory in the review by Raman \textit{et al.} [2], this is the most sensitive to the treatment of the hole. However, there are some other cases listed where experiment disagrees significantly with both types of calculation, making it difficult for one to whole-heartedly endorse the ``frozen orbital'' calculation. As a further step in settling this issue, we report here a measurement of the ratio of $\alpha _{K}$ values for the 127.5-keV $E3$ transition in $^{134}$Cs$^{m}$ and the 662-keV $M4$ transition in $^{137}$Ba. Our preliminary result, $\alpha _{K}$(Cs)/$\alpha _{K}$(Ba)=30.4(3), should be compared with the experimental ratio quoted in [2], 28.8(5), and with calculated ratios, 30.0 (hole) and 29.5 (no hole). The disagreement between experiment and theory is now removed and, furthermore, our result again points to the calculation that includes the hole. [1] N. Nica et al., Phys. Rev. C 70 (2004) 054305, [2] S. Raman et al., Phys. Rev. C 66 (2003) 044312. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q9.00007: Search for the Wobbling Mode in $^{171}$Ta D.J. Hartley, W.H. Mohr, J.R. Vanhoy, M.A. Riley, A. Aguilar, C. Teal, R.V.F. Janssens, M.P. Carpenter, F.G. Kondev, A.A. Hecht, T. Lauritsen, E.F. Moore, S. Zhu, M.K. Djongolov, M. Danchev, L.L. Riedinger, G.B. Hagemann, G. Sletten, P. Chowdhury, S.K. Tandel, W.C. Ma, S.W. Odegard Perhaps the strongest evidence for a nucleus possessing {\it stable} triaxial deformation is the observation of a wobbling excitation. Such exotic sequences have been confirmed in $\pi i_{13/2}$ bands of $N\approx 94$ Lu nuclei [1], and the region may extend to $N\approx 100$ in Hf nuclei. However, it has not been possible to confirm the presence of wobbling structures in the heavier isotopes [2]. In order to determine whether stable triaxiality plays a role in $N\approx 100$ nuclei, an experiment was conducted to search for the wobbling mode in $^{171}$Ta. High-spin states in $^{171}$Ta were produced in the $^{124}$Sn($^{51}$V,$4n$) reaction and the $\gamma$ rays were detected with Gammasphere. Although the $i_{13/2}$ band was extended to (101/2), no wobbling structure was identified. The implications of this result on the region of triaxiality will be discussed. [1] S.W. Odegard {\it et al.}, Phys. Rev. Lett. {\bf 86}, 5866 (2001). [2] D.J. Hartley {\it et al.}, Phys. Lett. B {\bf 608}, 31 (2005). [Preview Abstract] |
Monday, April 24, 2006 2:54PM - 3:06PM |
Q9.00008: Full major-shell calculation for states that are degenerate in a single-$j$-shell calculation Alberto Escuderos, Larry Zamick, Shadow Robinson In a previous work~\footnote{A.~Escuderos, B.F.~Bayman, L.~Zamick, and S.J.Q.~Robinson, Phys. Rev. C {\bf 72}, 054301 (2005)}, we explained why certain states were degenerate in the single $j$ shell for an interaction in which the isospin $T=0$ two-body matrix elements were set to zero. The degeneracy splitting was recovered by reintroducing the full interaction. In this work, we perform a full $fp$-shell calculation with the FPD6 interaction to obtain these energy splittings; the interaction obtained by setting the $T=0$ matrix elements to zero but keeping the $T=1$ ones unchanged will be called T0FPD6. Comparing the results with FPD6 and T0FPD6, we can see that most of the splitting in a complete shell calculation (but not all) comes from the $T=0$ part of the interaction. For example, the $(9^+_1-10^+_1)$ splitting in $^{44}$Ti is 1.214~MeV for FPD6, but it is only 0.094~MeV for T0FPD6. In $^{47}$V, the $(29/2^-_1-31/2^-_1)$ splitting is 0.780~MeV with FPD6, in agreement with the experimental value of 0.765~MeV, but T0FPD6 yields only 0.072~MeV. In general, we observe a continuity in the splittings between the single-$j$ and the full-$fp$ calculations; only in two cases we see an inversion of the states. These two cases involve low angular momentum states ($1/2^-$ in $^{43}$Sc and $3^+$ in $^{44}$Ti), for which there tends to be much more configuration mixing. [Preview Abstract] |
Session Q10: Rare B Decays
Sponsoring Units: DPFChair: Brendan Casey, Brown University
Room: Hyatt Regency Dallas Cumberland C
Monday, April 24, 2006 1:30PM - 1:42PM |
Q10.00001: Search for the radiative leptonic decay $B \rightarrow \gamma \ell\bar{\nu_{\ell}}$ Gregory Dubois-Felsmann We present the results of a search for charged $B$ meson decays into $\gamma \ell \bar{\nu_{\ell}}$, where $\ell = e, \mu$. We use a sample of approximately 232 million $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance by the BaBar detector at the PEP-II asymmetric-energy $B$~Factory at SLAC. This decay mode is related to the theoretically clean purely leptonic decay, but with a larger branching fraction due to the lack of helicity supression. An observation of this decay could be used either to evaluate the $B$ meson pseudoscalar decay constant $f_B$ or, with an independent determination of $f_B$, to test theoretical models of charmless $B$ decays. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q10.00002: Measurement of exclusive $B\rightarrow X_u l\nu$ branching fractions using semileptonic tags Shenjian Chen Using 210 fb$^{-1}$ of $\Upsilon(4S)$ data collected with the BABAR detector at the PEP-II storage ring, we report the result of a measurement of branching fractions of exclusive $B\to X_u\ell\nu$ decays. The accompanying $B$ mesons are tagged with semileptonic $B\to D^{(*)}\ell\nu$ decays. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q10.00003: Search for $B^0\rightarrow K^{*0}K_{\rm S}^0$ decay at BaBar Stephen Foulkes We present the result of a search for rare decays of $B$ mesons into $K^{*0}K_{\rm S}^0$ where $K^{*0}\rightarrow K^+\pi^-$ and $K_ {\rm S}^0\rightarrow \pi^+\pi^-$. We use a sample of approximately 227 million B-meson pairs recorded at the $\Upsilon(4S)$ resonance by the BaBar detector at the PeP-II $B$ Factory at SLAC. This decay mode provides input to theoretical studies of rare $B$ decays using flavor- symmetry or factorization methods. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q10.00004: Search for the rare decays $B\rightarrow \rho\gamma$ and $B^0\rightarrow\omega\gamma$ Karsten Koeneke Rare $B$ decays that follow a $b\to d\gamma$ transition are sensitive to the ratio $|V_{td}/V_{ts}|$ and are a promising probe for new physics. Decays of this type are most easily accessible through the rare decays $B\to\rho\gamma$ and $B^0\to\omega\gamma$. We present preliminary results of a search for these decays in a sample of approximately 300 million $B\bar{B}$ pairs collected with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q10.00005: Search for rare flavor-changing and electroweak penguin decays of the $B^0_s$ meson Ralf Bernhard Using 1 fb$^{-1}$ of data collected with the D\O\ detector in Run II of the Tevatron, limits are presented for searches for the rare flavor changing neutral current decay $B^0_s \rightarrow \mu^+ \mu^-$, as well as $B^0_s \rightarrow \mu^+ \mu^- \phi$. The former decay mode is particularly sensitive to supersymmetric extensions of the Standard Model. For the latter mode, a measurement of the branching ratio could validate the prediction of the Standard Model. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q10.00006: Lepton-flavour violating decays, $\tau\rightarrow l\pi^0/\eta/\eta^{\prime}$ Sanjay Swain Searches for lepton-flavor violating decays of $\tau$ leptons will be presented, with emphasis on channels $lM^{0}$ where $l$ is an electron or muon and $M^{0}$ is a $\pi^{0}$, $\eta$ or $\eta{'}$ meson. The analyses use data collected in $e^{+}e^{-}$ collisions at a centre-of-mass energy of 10.58~GeV with the BABAR detector at the PEP-II storage rings. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q10.00007: Search for Lepton Flavor Violation in $\Upsilon$ Decays William Love Using the data collected with the CLEO III detector at CESR we report on the first search for Lepton Flavor Violation in the decays of the $\Upsilon (1S)$, $\Upsilon (2S)$, and $\Upsilon(3S)$ resonances. After describing the various components of our unbinned maximum-likelihood fit, we present fits to background data, signal Monte Carlo, and signal data. The discovery of LFV in $\Upsilon$~decays could be explained by low-mass quantum gravity, Abdus-Salam leptoquarks, or neutrino oscillations arising in SUSY models. [Preview Abstract] |
Monday, April 24, 2006 2:54PM - 3:06PM |
Q10.00008: Hadronic spectrum of the $\tau^-\rightarrow \pi^-\pi^0\nu$ decay Rahmat Rahmat We describe a study of the invariant mass spectrum of the hadronic system in the $\tau^- \to \pi^-\pi^0\nu$ decay, using the BaBar detector at SLAC. We describe how the $\pi^-\pi^0$ spectral function inferred from the invariant mass spectrum can be used as a test of the Conserved Vector Current hypothesis. We also discuss the implications of our study in estimating the hadronic contribution to the muon anomalous magnetic moment. [Preview Abstract] |
Session Q11: Simulations of Binary Black Hole Mergers
Sponsoring Units: GGRChair: Carlos Lousto, The University of Texas at Brownsville
Room: Hyatt Regency Dallas Cumberland E
Monday, April 24, 2006 1:30PM - 1:42PM |
Q11.00001: Accurate Evolutions of Orbiting Black Hole Binaries Without Excision Yosef Zlochower, Manuela Campanelli, Carlos Lousto We present a new technique for evolving moving black holes without excision. Our technique, which is based on a regularization of the standard `puncture' approach to the BSSN evolution system, allows for stable evolution of orbiting black-hole binaries. We used this technique to evolve a set of pre-ISCO binaries and show the resulting waveforms as well as the tracks of the individual horizons. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q11.00002: Unequal-Mass Binary Black Hole Inspirals Deirdre Shoemaker, Frank Herrmann, Pablo Laguna We present results from fully nonlinear simulations of inspiralling, unequal mass binary black holes. We show waveforms of the dominant $l=2,3$ modes. The power spectrum of these modes yields insight on how the mass ratio in a binary impacts the degree of complexity of the emitted waveforms. In addition, we provide approximate estimates of energy and angular momentum radiated as well as kick velocities from gravitational radiation recoil. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q11.00003: Binary Black Hole Evolutions with Moving Punctures: Methods and Numerical Codes. Pedro Marronetti, Wolfgang Tichy, Bernd Bruegmann Binary Black Holes are strong emitters of gravitational waves and their behavior during the last few orbits can only be accurately described by full general relativistic simulations. Here we present the numerical techniques and programs used for the simulation of such binaries. Our evolutions are performed using the BSSN formulation and the recently introduced ``moving punctures'' technique. We present the details of our numerical setup, as well as gauge choices and boundary conditions. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q11.00004: Binary Black Hole Evolutions with Moving Punctures: Final orbits, merger and ringdown. Wolfgang Tichy, Pedro Marronetti, Bernd Bruegmann We present results of simulations of black hole binaries in circular orbits covering the last orbit and the merger and ringdown phases. These simulations are performed using the BSSN formulation and the recently introduced ``moving punctures'' technique. We compare different implementations of this technique and discuss how they affect convergence. We also cover in detail the results of our orbiting punctures simulations and their dependence on grid size and resolution. In addition, we discuss quality control curves and constraint satisfaction. [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q11.00005: How to move a black hole James van Meter, John Baker, Joan Centrella, Dae-Il Choi, Michael Koppitz Recent demonstrations of uncexcised, puncture black holes traversing freely across computational grids represent a revolutionary advance in numerical relativity. Stable and accurate simulations of multiple orbits, and their radiated waves, have resulted. This capability is critically undergirded by careful choices of gauge and formulation of the evolution equations. Here we describe the relevant techniques, analytically justify their necessity, and numerically demonstrate their efficacy. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q11.00006: Gravitational waveforms from equal mass binary black hole systems Michael Koppitz, John Baker, Dae-Il Choi, Joan Centrella, James van Meter Using recently developed techniques for evolving binary black hole systems we report on evolutions of black holes through orbits, merger, and subsequent ringdown. The evolutions show stability and accuracy such that we can report convergent waveforms and energy conservation. The influence of the initial data is evaluated, the dependency of the dynamics from the initial separation tested, and a heuristic waveform template presented. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q11.00007: Gravitational Radiation Recoil from Merging Massive Black Hole Binaries Dae-Il Choi, John Baker, Joan Centrella, Michael Koppitz, Jim van Meter One key area of interest for numerical relativity is calculation of kicks in merging massive black hole binaries where linear momentum, as well as energy and angular momentum, is lost due to asymmetric radiation of gravitational waves. As a result, the merger remnant receives a kick also known as gravitational rocket effect. High kick velocities, comparable or higher than escape velocites of the host structures, will provide a critical input to our understanding of various aspects of massive black hole evolutions in the universe. I describe a recent calculation of the kick velocities from simulations of the merging massive black hole binaries. Starting from reasonable initial data for quasi-circular configurations of non-equal mass and non-spinning black hole binary, simulations are carried out through merger and ringdown. From mergers with different mass ratio and different initial separations, kick velocities are estimated based on gravitational waveforms extracted in the wave-zone. I discuss astrophysical implications of the magnitude of the kicks. [Preview Abstract] |
Session Q12: Baryons and B Lifetime Studies
Sponsoring Units: DPFChair: William T. Ford, University of Colorado
Room: Hyatt Regency Dallas Cumberland F
Monday, April 24, 2006 1:30PM - 1:42PM |
Q12.00001: Production of Charm Baryons in CDF II Elena Vataga Using the data collected with the CDF Run II detector preliminary results on ground state charm baryon $\Lambda_{c}^{+}$ and $\Sigma_{c}^{++,0}$ will be presented. The results are based on a large data sample made available by the displaced track trigger. The results on $\Sigma_{c}^{++,0}$ are the measurements made at Tevatron hadron collisions for the first time. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q12.00002: BaBar Searches for Double Charm Baryons Adam Edwards We present the results of searches for $\Xi_{cc}^+\rightarrow \Lambda_c^+ K^- \pi^+$ and $\Xi_{cc}^{++}\rightarrow \Lambda_c^+ K^- \pi^+ \pi^+$. The decay $\Lambda_c(2880)\rightarrow \Lambda_c^+ \pi^- \pi^+$ is used as a control and reference mode. We search wide mass regions for the $\Xi_{cc} ^+$ and \Xi_{cc}^{++}$ baryons that include several previously reported signals and theoretical predictions. Experimentally observing double charm baryons is a major step in scrutinizing predictions involving diquarks in theoretical QCD. Our data set was collected with the BaBar detector at the PEP-II $e^+e^-$ storage rings and consists of 210 fb$^{-1}$ collected on the $\Upsilon(4S)$ resonance, and 22 fb$^{-1}$ collected approximately 40 MeV below this resonance. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q12.00003: Studies in heavy baryon chiral perturbation theory T. Brian Bunton We investigate heavy baryon chiral perturbation theory (HBChPT) and its convergence properties by considering different power counting schemes and higher order terms. We apply these modifications to strong decays of the decuplet baryons and to axial currents of the octet baryons. Then we turn to weak decays of the octet and decuplet. We hope to improve the extraction of low energy constants of the theory with the goal of providing improved predictions for octet and decuplet baryon observables, including those involved in hypernuclear decay. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q12.00004: Numerical calculations of electromagnetic contributions to baryon masses Phuoc Ha We calculate numerically the electromagnetic contributions to the baryon masses which we analyzed recently using the heavy-baryon approximation in chiral effective field theory and methods developed in our earlier analyses of the baryon masses and magnetic moments. We find that the effects of the quark masses, the Coulomb and moment-moment interactions, and the mesonic corrections account fairly well for a pattern of coefficients in a mass-difference Hamiltonian that describes well the accurately known baryon mass splittings. [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q12.00005: $B^+$, $B^0$, $B^0_s$, $\Lambda_B$ lifetimes and lifetime ratios. Chunlei Liu We present new, high-statistics measurements of b hadron lifetimes from exclusive decays containing a $J/\psi$ selected using a dimuon trigger in CDF. The analysis uses about 800 pb$^{-1}$ of data from Run II of the Tevatron collider. In addition to the channels $B^+ \rightarrow J/\psi K^+$, $B^0 \rightarrow J/\psi K^{0*}$, $B^0\rightarrow J/\psi K^0_s$, which are well measured at B factories, we measure lifetimes of $\Lambda_b$ and $B_s^0$, (unique to the Tevatron) in the channels $B^0_s\rightarrow J/\psi\phi$ and $\Lambda_b \rightarrow J/\psi\Lambda^0$. Systematic errors in the ratios of lifetimes are minimized by the consistent use of the $J/\psi$ vertex across all decay channels, to estimate proper decay time. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q12.00006: Monte Carlo Free Estimation of the $B^+$ Meson Lifetime Using a Hadronic Decay Mode Azizur Rahaman We present a new measurement of the $B^{+}$ meson lifetime from exclusive decays ($B^{+} \rightarrow \bar{D^0}\pi^{+}$), selected using CDF's hadronic B trigger from about 800 pb$^{-1}$ of data from Run II of the Tevatron collider. The bias induced by this trigger is corrected on an event-per-event basis, using observed kinematic event variables, with no dependence on Monte Carlo simulation. The analysis is complementary to CDF's previously published analyses, which uses an efficiency curve obtained from simulation, and has independent systematic uncertainties. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q12.00007: Measurement of the $\Lambda_b$ lifetime in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV Michael Schmidt The lifetime of the $\Lambda_b$ baryon is presently the most interesting of all $b$-hadron lifetimes, and at the same time the least well known experimentally. We study the lifetime of the $\Lambda_b$ baryon using $\Lambda_b \to \Lamdbda_c^+\pi^+$ decay mode in 360~pb$^{-1}$ of CDF data. Our $\Lambda_b \to \Lamdbda_c^+\pi^+$ sample has in excess of $1400$ events and is the largest sample of $\Lambda_b$ decays in existence. We study the effects of the trigger bias and the presence of physics backgrounds on the measurement of the lifetime of $\Lambda_b$. [Preview Abstract] |
Monday, April 24, 2006 2:54PM - 3:06PM |
Q12.00008: $\Lambda_b$ lifetime measurement using semileptonic decays at D\O Marcus Lewin Using approximately 1 fb$^{-1}$ of data collected by the D\O detector in Run II, a sample of over 2000 $\Lambda_b \rightarrow \Lambda_c \mu X (\Lambda_c \rightarrow K_s p)$ decays has been reconstructed. We present preliminary results of a measurement of the $\Lambda_b$ lifetime using this sample. [Preview Abstract] |
Monday, April 24, 2006 3:06PM - 3:18PM |
Q12.00009: Study of the form factor in semileptonic $\Lambda_b$ decays Abaz Kryemadhi We measure the $\Lambda_b$ baryon form factor using the exclusive decay ${\Lambda^0_b \rightarrow \Lambda^+_c \mu^- \bar{\nu}}$ followed by $\Lambda^+_c \rightarrow p^+ K^0_S$ and $K^0_S \rightarrow \pi^+ \pi^-$. The data sample corresponds to an integrated luminosity of approximately 1~fb$^{-1}$, recorded with the D\O\ detector in $p\bar{p}$ collisions at $\sqrt{s} =1.96$~TeV. We present a preliminary result on the Isgur-Wise slope. [Preview Abstract] |
Session Q13: Particle Searches II
Sponsoring Units: DPFChair: Beate Heinemann, University of Liverpool
Room: Hyatt Regency Dallas Cumberland G
Monday, April 24, 2006 1:30PM - 1:42PM |
Q13.00001: Minimal Supergravity with m$_0^2 <$ 0 Bryan Smith, Jonathan Feng, Arvind Rajaraman We extend the parameter space of minimal supergravity to negative values of m$_0^2$, the universal scalar mass parameter defined at the grand unified scale. After evolving to the weak scale, all scalars can be non-tachyonic with masses consistent with collider constraints. This region of parameter space is typically considered excluded by searches for charged dark matter, since the lightest standard model superpartner is a charged slepton. However, if the gravitino is the lightest supersymmetric particle, the charged slepton decays, and this region is allowed. This region provides qualitatively new possibilities for minimal supergravity, including spectra with light sleptons and very heavy squarks, and models in which the lightest slepton is the selectron. We show that the m$_0^2 <$ 0 region is consistent with low energy precision data and discuss its implications for particle colliders. These models may provide signals of supersymmetry in even the first year of operation at the Large Hadron Collider. [Preview Abstract] |
Monday, April 24, 2006 1:42PM - 1:54PM |
Q13.00002: Search for Multi-photon Signatures in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV Oleksiy Atramentov A preliminary cross section for the inclusive multiphoton production is presented, as measured by the Run II D\O\ detector at the Fermilab Tevatron $p\bar{p}$ collider. Photon candidates with transverse momenta greater than 15 GeV$/c$ and within the pseudorapidity of $|\eta| < 2.5$ are considered. Selection criteria for photon candidates as well as the estimation of background contributions from QCD and EW processes are presented. Event topologies with $\gamma\gamma\gamma+X$ in the final state which are relevant for fermiophobic Higgs boson searches in two Higgs doublet and triplet models are emphasized. Preliminary limits on the mass of fermiophobic Higgs boson are set. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:06PM |
Q13.00003: Search for Randall-Sundrum excitations of gravitons decaying into two photons for CMS at LHC Vladimir Litvin, H. Newman, M.-C. Lemaire The CMS detector discovery potential for resonant production of the massive Kaluza - Klein excitations predicted by the Randall- Sundrum model is studied. Full simulation and reconstruction are used to study the diphoton decay of Randall-Sundrum gravitons. For an integrated luminosity of 30 fb${}^{-1}$, the diphoton decay of Randall- Sundrum gravitons can be discovered at the 5$\sigma$ level for masses up to 1.61 ${}TeV/c^2$ for the case of weak coupling between graviton excitations and Standard model particles ($c=0.01$). Heavier resonances can be detected if the coupling is larger ($c=0.1$), with a mass reach of 3.95 ${}TeV/c^2$. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:18PM |
Q13.00004: Sensitivity to Contact Interactions from Quark Compositeness at CMS Selda Esen, Robert Harris CMS will measure dijets in proton-proton collisions at $\sqrt{s} =14$ TeV. The angular distribution of dijets as a function of invariant mass is sensitive to a contact interaction among quarks that could arise if quarks are not pointlike particles. The sensitive part of the angular distribution is measured by the dijet ratio: the number of dijet events with $|\eta|<0.5$ divided by the number of dijet events with $0.5<|\eta|<1.0$. As a function of dijet invariant mass, we present estimates of the dijet ratio for both the QCD background and a contact interaction signal. For integrated luminosities of 100 pb$^{-1}$, 1 fb$^{-1}$ and 10 fb$^{-1}$, we present CMS capability to exclude or discover contact interactions from quark compositeness. [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:30PM |
Q13.00005: Sensitivity to Dijet Resonances at CMS Kazim Gumus, Nural Akchurin, Selda Esen, Robert Harris CMS will measure the dijet mass spectrum in proton-proton collisions at $\sqrt{s}=14$ TeV and will search for narrow resonances. For an integrated luminosity of 1 fb$^{-1}$ the measured dijet mass spectrum of the QCD background is expected to extend from 0.3 to 6 TeV for jet $|\eta|<1$. For integrated luminosities of 100 pb$^{-1}$, 1 fb$^{-1}$ and 10 fb$^{-1}$, we present CMS capability to exclude or discover several models of narrow dijet resonances: excited quarks, axigluons or colorons, E6 diquarks, color octet techirhos, Randall-Sundrum gravitons, and new electoweak gauge bosons W' and Z'. [Preview Abstract] |
Monday, April 24, 2006 2:30PM - 2:42PM |
Q13.00006: Search for Heavy Right-handed Quarks in the Electron-Muon+X channel Marshall Collin Wolfe We present a search for new, heavy objects in the electron-muon channel at CDF using 300~$pb^{-1}$ of data. To probe the reach of the search, we set a cross section limit on a 300 GeV right handed down type quark predicted by Bjorken, Pakvasa and Tuan. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 2:54PM |
Q13.00007: Search for long-lived neutral particles Todd Admas We have performed a search for a relatively long-lived neutral particle using the D\O\ experiment. The particle is allowed to decay significantly away from the production (at least 5 cm), but still within the inner tracking detector. We search for a decay to two muons and missing energy, using the muon tracks to identify the displaced vertex. Background is found to be small and estimated from the data. We present the results of our search and a comparison to the limit set by NuTeV for dimuon events in the 3-15 GeV mass region. [Preview Abstract] |
Session Q14: History of Physics
Sponsoring Units: FHPChair: Robert H. Romer, Amherst College
Room: Hyatt Regency Dallas Cumberland I
Monday, April 24, 2006 1:30PM - 1:54PM |
Q14.00001: Was Nazi Germany on the Road to an Atomic Bomb after all? Harry Lustig The story of Germany’s efforts to develop a nuclear weapon during World War II is a much written about and contentious subject. However there has been agreement on one thing: by the end of the War the Germans had not achieved and were nowhere near to building a bomb. The dispute therefore has been about why Germany did not succeed. Now, from Germany, comes a challenge to this truth, in the provocative book Hitlers Bombe by Rainer Karlsch. The bombshell in Hitler’s Bombe is the assertion that German scientists developed and tested a primitive fission and fusion nuclear weapon in March 1945. Karlsch bases this claim on testimony of witnesses in 1962, previously secret Russian documents, and the results of soil tests carried out in 2004 and 2005. However the physics is very murky and it seems out of the question that Germany had enough Uranium 235 or produced any Plutonium for a bomb. Hitlers Bombe also makes other, better documented and more credible revisionist assertions. These include the claim that the Nazis did continue to try to build a bomb after 1942 and that not Werner Heisenberg, but Kurt Diebner and Walther Gerlach were then the leaders of the German Uranium project. Karlsch’s book therefore deserves more attention from physicists and historians than it has received in the United States. [Preview Abstract] |
Monday, April 24, 2006 1:54PM - 2:18PM |
Q14.00002: Einstein and Oskar Klein: The Fifth Dimension as a Bridge across Quantum Chasms Paul Halpern In the mid 1920s, various physicists grappled with the underlying mechanisms for quantization. While at Ann Arbor, Oskar Klein developed a deterministic theory based upon the assumption of an undetectable fifth-dimension. With the rise of modern quantum mechanics, Klein, along with his colleagues, embraced the idea of wave functions acting in Hilbert space, and abandoned, for a time, the concept of an extra physical dimension. During the same period, Einstein, in contrast, began to explore five-dimensional unified field theories---first along with Walther Mayer, then with Peter Bergmann and Valentine Bargmann. This talk will explore connections---conceptual and philosophical---between Einstein's and Klein's theories, analyze the differences, examine the correspondence between the two theorists, and delve into the reasons each came to embrace and abandon the idea of the fifth dimension. [Preview Abstract] |
Monday, April 24, 2006 2:18PM - 2:42PM |
Q14.00003: SED Alumni---breeding ground for scientists Benjamin Bederson In 1943 the US Army established the Special Engineering Detachment (SED), in which mostly drafted young soldiers possessing some scientific credentials (though usually quite minimal) were reassigned from other duties to the Manhattan Project to assist in various research and development aspects of nuclear weapons. The Los Alamos contingent, never more than a few hundred GIs, worked with more senior scientists and engineers, often assuming positions of real responsibility. An unintended consequence of this circumstance was the fact that being in the SEDs turned out to be a fortuitous breeding ground for future physicists, chemists, and engineers. SEDs benefited from their close contacts with established scientists, working with them side by side, attended lectures by luminaries, and gained invaluable experience that would help them establish academic and industrial careers later in life. I will discuss some of these individuals (I list only those of whom I am personally aware). These include Henry ``Heinz'' Barschall*, Richard Bellman*-RAND Corporation, Murray Peshkin-ANL, Peter Lax-Courant Institute, NYU, William Spindel*-NRC,NAS, Bernard Waldman- Notre Dame, Richard Davisson*-U of Washington, Arnold Kramish- RAND, UNESCO, Josef Hofmann- Acoustic Research Corp, Val Fitch- Princeton U. *deceased [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:06PM |
Q14.00004: Rosenfeld, Bergmann, and the Invention of Constrained Hamiltonian Dynamics Donald Salisbury Significant progress in the invention of constrained Hamiltonian dynamics was made by Leon Rosenfeld in a paper he published in the Annalen der Physik in 1930. He applied his general formalism to general relativity with electrodynamical field and Dirac electron sources. His proposed Hamiltonian will be compared and contrasted with an independently developed precursor investigated by Peter Bergmann and collaborators in 1949-50. [Preview Abstract] |
Monday, April 24, 2006 3:06PM - 3:18PM |
Q14.00005: Historic Patterns in Astronomical Incomprehension Virginia Trimble Because astronomy is old, it has had a chance to display some very prolonged battles in the war between ideas (theories) and observations (data) that we call science. It is possible to discern two major patterns -- data leading vs. ideas leading -- and very short to very long durations of the events that eventually led to understanding. A variant has the community converging with vigor around a wrong answer (gamma ray bursters are a recent example). The talk will explore some of the author's favorite examples of each pattern. These include the rapid basic understanding of quasars and pulsars vs. the extremely long times required to figure out the solar corona and pulsating variable stars. Among the cases where theory has led via prediction, discovery was almost immediate for 21 cm radio emission and superluminal motion in quasars, but very slow for fluctuations in the cosmic microwave background radiation, certain kinds of polarization, and (surely a record never to be broken) heliocentric parallax. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700