Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session K8: Hadronic Physics I |
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Sponsoring Units: DNP Chair: Barry Berman, George Washington University Room: Delaware B |
Sunday, February 14, 2010 3:30PM - 3:42PM |
K8.00001: Polarization Observable $E$ in the $p(\gamma, \pi^+)n$ Reaction Steffen Strauch The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable $E$ for the reaction $\vec \gamma \vec p \to \pi^+n$ has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. The extracted polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses. [Preview Abstract] |
Sunday, February 14, 2010 3:42PM - 3:54PM |
K8.00002: Near Threshold Pion Electroproduction at High $Q^2$ Puneet Khetarpal Near threshold pion electroproduction as a function of $Q^2$ can be written in terms of new form factors. These new generalized form factors $G_{1}^{\pi N}$ and $G_{2}^{\pi N}$ have been predicted using light cone sum rules in the chiral limit for the reactions $ep \to eN\pi$ in the $Q^2$ 1-10 $\textrm{GeV}^2$ range. It's an experiment at Jefferson Lab that has been conducted using the CLAS spectrometer to measure near threshold pion electroproduction as a function of $Q^2$. The differential cross sections and the extracted electromagnetic multipoles and form factors will be presented. [Preview Abstract] |
Sunday, February 14, 2010 3:54PM - 4:06PM |
K8.00003: Photoproduction of the exclusive $\gamma p \to K^{*+}Y$ reaction ($Y=\Lambda$ or $\Sigma^0$) at CLAS Wei Tang, Dustin Keller, Kenneth Hicks The reaction $\gamma p \to K^{*+} \Lambda$ has been measured at Jefferson Lab using the CLAS detector with tagged photons in the energy range of 1.6-3.8 GeV. Previously reported data for this reaction are either preliminary or were done decades ago with less precision. The $K^{*+}$ was identified directly from its decay products, and the $\Lambda$ of $\Sigma^0$ final state was determined from the technique of missing mass. Cross sections for this reaction will be presented, along with preliminary results for the Lambda recoil polarization. Calculations for this reaction have been published from theoretical models, indicating that the cross sections are sensitive to whether a scalar meson $J^P = 0^+$ with a strange antiquark may exist. Suggestions for the physical interpretation of these data will be briefly discussed. [Preview Abstract] |
Sunday, February 14, 2010 4:06PM - 4:18PM |
K8.00004: Cascade Spectroscopy and Recent Photo-production Results from CLAS Dennis Weygand Doubly-strange baryon resonances provide insights into the baryon structure. The SU(3) flavor symmetry implies that for every N$^*$ and $\Delta^*$ resonance, there will be a corresponding $\Xi^*$ (cascade resonance). Therefore, one can investigate the non-strange baryons at energies above approximately 1.5 GeV via the cascade spectra where many N$^*$ and $\Delta^*$ resonances are broad and overlapping, and thus requiring complex coupled channel partial wave decomposition for analysis. The cascade resonances in the range from 1.5 to 2.5 GeV however are narrower and more readily observed; properties can be determined from mass spectra and moment analysis. Preliminary results from a recent high-luminosity and high energy ($\sim 5.4$ GeV) photo-production experiment at the Jefferson Laboratory CLAS detector will be presented. [Preview Abstract] |
Sunday, February 14, 2010 4:18PM - 4:30PM |
K8.00005: Search for Strangeonia in Photoproduction using CLAS Mukesh Saini The HyCLAS experiment at Jefferson Lab is a program to search for new and unusual mesons produced via photoproduction. The strangeonia sector is poorly known and a main component of this program is a search for new strangeonium states. The reaction $\gamma~ p \rightarrow p ~\phi~ \eta$ is an ideal channel to look for strangeonium states due to the strangeness content of both the $\phi$ and $\eta$. The data was acquired at the JLAB CLAS facility using a 4 - 5.5 GeV tagged photon beam. The $\phi$ meson is identified via the $K^+ K^- $ decay. The recoil proton is observed in the CLAS spectrometer and the $\eta$ meson is identified through the missing mass. Also of interest is the search for strangeonia decaying to $\phi \pi^0$ and $\phi \omega$. These channels are OZI suppressed for $q \bar q$ mesons and an observation of a meson decaying to these channels would provide a strong evidence of mesons beyond $q \bar q$. Preliminary results describing the data quality, kinematics and dynamics will be shown. [Preview Abstract] |
Sunday, February 14, 2010 4:30PM - 4:42PM |
K8.00006: Measurement of Single Target-Spin Asymmetry in Semi-Inclusive Charged Pion Electroproduction on a Transversely Polarized $^3$He Target Chiranjib Dutta We measured the neutron target single spin asymmetry in the semi-inclusive deep inelastic $^3He^{\uparrow}(e,e'\pi^{\pm})X$ reaction using a transversely polarized $^3$He target. The experiment acquired data in Hall A at Jefferson Lab using a 40 cm long polarized $^3$He target and an electron beam of 5.9 GeV. This first measurement on neutron transversity focuses on the valence quark region, $x = 0.13\sim 0.41$, at $Q^2=1.31\sim3.10~(\mathrm{GeV}/c)^2$. Pions were detected in the left high-resolution spectrometer in coincidence with the scattered electrons detected by the BigBite spectrometer. The data from this experiment, when combined with world data, will provide constraints on the Transversity, Sivers distribution functions and Collins fragmentation functions of both $u$-quark and $d$-quark in the valence region. A brief summary of the ongoing analysis and preliminary results will be presented. [Preview Abstract] |
Sunday, February 14, 2010 4:42PM - 4:54PM |
K8.00007: Coherent $\pi^+$ Photoproduction on $^3$He Rakhsha Nasseripour, Barry Berman Comparing an elementary meson-production process on a free nucleon with the same process inside a nucleus has been an interesting problem in nuclear physics. Studying these processes are useful in developing our understanding of nuclear structure and the long-range part of the nucleon-nucleon interaction described by the one-pion-exchange model. In the present analysis, we have measured the differential cross section for the $\gamma$$^3$He$\rightarrow \pi^+ t$ reaction channel. Studying this channel is ideal for understanding the interaction of pions with nuclei and for searching for possible effects mediated by nucleon resonances in nuclear matter. The $^3$He target contains the lightest nucleus on which one can observe coherent (elastic) $\pi^+$ photoproduction with charge exchange that also leads to a well defined final state that can be easily identified. This reaction was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.35 to 1.55 GeV were incident on a cryogenic liquid $^3$He target. The differential cross sections for the $\gamma$$^3$He$\rightarrow \pi^+ t$ reaction were measured as a function of photon-beam energy and pion-scattering angle in the center-of-mass frame. Our results will be presented and discussed. [Preview Abstract] |
Sunday, February 14, 2010 4:54PM - 5:06PM |
K8.00008: ABSTRACT WITHDRAWN |
Sunday, February 14, 2010 5:06PM - 5:18PM |
K8.00009: The Photoproduction of $\Lambda $*(1520) Zhiwen Zhao The photoproduction of $\Lambda $*(1520) on both the proton and neutron have been studied by using CLAS eg3 run data set. The reactions are $\gamma $d $\to $ K$^{+}\Lambda $*(n) and $\gamma $d $\to $ K$^{0}\Lambda $*(p) with $\Lambda $* $\to $ pK$^{-}$. Both preliminary total and differential cross sections have been extracted in the photon energy region 1.75GeV $<$ E$_{\gamma } \quad <$ 5.50GeV. This is the first time that the photoproduction of $\Lambda $*(1520) on the neutron is reported. And we will extend the results on the proton to higher energies than in previous studies. [Preview Abstract] |
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