Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session BG: Strange Matter |
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Chair: Zein-Eddine Meziani, Temple University Room: Jewett Ballroom C |
Friday, October 24, 2008 8:30AM - 8:42AM |
BG.00001: Determining the Nucleon's Neutral Weak Axial Form Factor $G^{e(T=1)}_{A}$ Using Quasi-Elastic Electron Scattering from a Deuterium Target Colleen Ellis The $G^{0}$ collaboration has taken data using the Jefferson Lab high- luminosity polarized electron beam to measure the parity-violating asymmetry of elastically and quasi-elastically scattered electrons from cryogenic proton and deuterium targets. This asymmetry, arising from the interference between the electromagnetic and neutral weak interactions and which may be as small as a few ppm, provides a means to determine the strange quark contribution to the proton electric and magnetic form factors, $G^{s}_{E}$ and $G^{s}_{M}$, and the neutron's neutral weak axial form factor, $G^{e(T=1)}_{A}$. The asymmetry seen in quasi-elastic electron scattering from deuterium is predominantly sensitive to the isovector part of $G^{e}_{A}$, which is one of the dominant uncertainties in the present experimental determination of $G^{s}_{E}$ and $G^{s}_{M}$ at lower momentum transfer. The status, method, and on-going analysis of the data quality, behavior of asymmetries, and systemic errors involved in the determination of $G^{e}_{A}$ at $Q^{2}$ of 0.23 $GeV^{2}$ and 0.63 $GeV^{2}$ will be presented. [Preview Abstract] |
Friday, October 24, 2008 8:42AM - 8:54AM |
BG.00002: Determining $G_E^s$ and $G_M^s$ from parity violating asymmetry measurements at $Q^2= 0.23$, $0.63$ GeV$^2$ Mathew Muether The G$^0$ experiment recently utilized the high luminosity polarized electron beam at Jefferson Lab to measure parity-violating asymmetries in backward scattered electrons from cryogenic hydrogen and deuterium targets at momentum transfers, $Q^2$, of $0.23$ and $0.63$ GeV$^2$. These asymmetries, arising from the interference of the electromagnetic and neutral weak interactions, are only a few tens of parts-per-million. A dedicated toriodal superconducting magnetic spectrometer, and fast counting electronics provided the required particle identification and measurement precision. These data together with previous results, including the G$^0$ forward angle measurement [1], allow the determination of the strange electric and magnetic nucleon form factors, $G_E^s$ and $G_M^s$ at the respective $Q^2$ values. The current status of our analysis to determine these values will be presented. {\linebreak} [1]D.S. Armstrong et al. (G0), {\it Phys. Rev. Lett.} {\bf 95}, 092001 (2005). [Preview Abstract] |
Friday, October 24, 2008 8:54AM - 9:06AM |
BG.00003: Searching for Strangelets in Lunar Soil at $10^{-17}$ Sensitivity Level using the Accelerator Mass Spectrometry Technique Ke Han The theoretical existence of Strange Quark Matter (SQM) has been postulated for over three decades. A wide range of experimental searches for strangelets (i.e. small lumps of SQM with baryon number less than $10^6$) have been conducted but all failed to give a definite answer to the existence of SQM. Our experiment searches for strangelets in lunar soil, where the predicted strangelet concentration is about $10^5$ times higher than that on Earth. The lunar soil sample is accelerated to 102 MeV using the tandem Van-de-Graaff accelerator at Yale University and analyzed using the accelerator mass spectrometry technique. We find no strangelet signal in the mass range 42 to 70 amu. The single event sensitivity limit for the existence of strangelet with electric charge equal to 8, 9, or 6 (strange oxygen, fluorine, or carbon) in our covered mass range is about $10^{-17}$ strangelet per normal atom. [Preview Abstract] |
Friday, October 24, 2008 9:06AM - 9:18AM |
BG.00004: $\phi$(1020) Photo-production in Neutral Decay Channel $\gamma p \rightarrow p'\phi \rightarrow p'K_S K_L$ Heghine Seraydaryan, Moskov Amarian, Hovhannes Baghdasaryan, Larry Weinstein, Gagik Gavalian Using photo-production data on hydrogen target collected with CLAS detector at Thomas Jefferson National Accelerator Facility the $\phi$(1020) meson production cross-sections in the neutral decay channel $\phi \rightarrow K_S+K_L$ is obtained for the first time. The measured cross-section shows difference from the charged channel decay ($\phi \rightarrow K_++K_-$). In this talk we present the cross-section and the $t$ - slope for wide photon energy range E$_\gamma$= 1.6-2.6 GeV. [Preview Abstract] |
Friday, October 24, 2008 9:18AM - 9:30AM |
BG.00005: Nuclear Transparency of Kaons (K+) Nuruzzaman Quantum Chromo Dynamics (QCD) is the fundamental theory of the strong force. The transition from nucleons and mesons to the quarks and gluons of QCD can be studied by looking for the onset of phenomena predicted by QCD, such as Color Transparency (CT). CT is the disappearance of final (initial) state interactions for hadrons produced in exclusive processes at high momentum transfers. An experiment to measure the transparency of pions, in search of CT was completed in Dec 2004 at JLab in Hall C. The same set of data also has a considerable sample of kaons that can be used to study the transparency of kaons. Kaon transparency via electro-production has not been studied before and will provide useful information regarding the nature of the transition from quarks to hadrons. In addition, this data helped us investigate the anomalous strangeness transparency reported for kaon-nucleus scattering data. We have extracted the kaon transparency by comparing the electro-production of kaons from various nuclear targets to electro-production from hydrogen which is similar to the technique used to extract pion transparency. Preliminary results from this analysis will be presented. [Preview Abstract] |
Friday, October 24, 2008 9:30AM - 9:42AM |
BG.00006: Photoproduction of Neutral Kaons on Deuterium Kabi R. Bantawa, D.M. Manley The $\gamma n \to K^0 \Lambda$ reaction on a liquid deuterium target was measured in the A2 Hall of the MAMI-C electron accelerator facility at the Institut f\"ur Kernphysik in Mainz, Germany. An incident electron beam of energy 1.5~GeV was directed on a 10-$\mu$m copper radiator to produce a {\it bremsstrahlung} photon beam that was tagged using the Glasgow Photon Tagger. The final-state $K^0$ and $\Lambda$ were identified by their decays $K^0 \to 2\pi^0$ and $\Lambda \to \pi^0 n$, respectively. These three $\pi^0$s were reconstructed by detecting and analyzing the six photons resulting from the $\pi^0$ decays using the Crystal Ball multiphoton spectrometer and the TAPS detector as a forward wall. This combined detector system covered nearly $4\pi$ in solid angle. Kinematic fitting was used to select good events. This reaction is expected to shine light on isospin-1/2 nucleon resonances in the 1.7-GeV mass range. An experimental overview and preliminary results for differential and integrated cross sections will be presented. [Preview Abstract] |
Friday, October 24, 2008 9:42AM - 9:54AM |
BG.00007: Partial-wave analysis of $K^+$ nucleon scattering William Gibbs, Roberto Arceo We have performed a partial-wave analysis of K$^+$-nucleon scattering in the beam momentum range from 0 to 1.5 GeV/c addressing the uncertainties of the results and comparing them with previous analyses. A careful treatment of the reaction threshold behavior is particularly important to avoid false indications of resonances. We find a T=0 scattering length which is not consistent with zero, contrary to what has been claimed by other analyses. The T=0 phase shifts for $\ell>0$ are found to be consistent with a pure spin-orbit potential. Some indications for the production of a T=0 pentaquark with spin-parity D5/2+ will be discussed. [Preview Abstract] |
Friday, October 24, 2008 9:54AM - 10:06AM |
BG.00008: Preliminary results from Jefferson Lab HKS experiment Lulin Yuan The HKS experiment at Jefferson Lab aims to obtain high resolution hypernuclear spectroscopy from light to medium-heavy mass region. A nice feature of the experiment is that the HKS spectrometer system has a kinematics coverage which allows the experiment to obtain high precision information about the absolute binding energy of the hypernuclear ground states, in addition to the excitation energy of the hypernuclear excited states. We have carried out extensive calibration for the optics and kinematics of the spectrometer system to further improve the energy resolution and the precision of the binding energy determination. In this talk, I will present the most updated spectra of $^{12}_\Lambda$B, $^{28}_\Lambda$Al and $^{7}_\Lambda$He. The experimental setup and spectrometer calibration procedure will also be described. [Preview Abstract] |
Friday, October 24, 2008 10:06AM - 10:18AM |
BG.00009: The GlueX Experiment at Jefferson Lab Curtis Meyer The GlueX experiment is part of the Jefferson Lab 12-GeV upgrade and is a large solid angle device for the detection of photons and charged particles. GlueX will search for gluonic excitations of mesons (exotic hybrids) using linearly polarized 9 GeV photons incident on a hydrogen target. The experiment has been designed to be sensitive to the expected mass and decay modes of hybrid mesons. With this capability, the experiment will be able to map out several nonets of exotic hybrids and make solid comparisons to both lattice predictions as well as other QCD-inspired model predictions. Beyond the core program of hadron spectroscopy, the experiment will also be able to carry out measurements of photon interactions on various targets. Both the core physics as well as interesting measurements that will be possible using GlueX will be presented. [Preview Abstract] |
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