Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session P8: Hadronic Physics II |
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Sponsoring Units: DNP Chair: Volker Burkert, Thomas Jefferson National Accelerator Facility Room: Delaware B |
Monday, February 15, 2010 10:45AM - 10:57AM |
P8.00001: Mesurements of Spin-Orbit Correlations at CLAS Harut Avakian The single-spin asymmetries (SSAs) in semi-inclusive DIS have emerged as a powerful tool to access transverse momentum distributions of partons. SSAs enable measurements of some essentially unexplored physical observables, including correlations of the transverse momentum of quarks and the spin of quarks and hadrons. New data has been collected at CLAS in JLab in 2009 on longitudinally polarized NH3 and ND3 targets, which increases by an order of magnitude all available data collected so far with polarized targets in the valence region. In this talk we present the latest studies of transverse spin effects accessible with longitudinally polarized target and discuss newly released results. [Preview Abstract] |
Monday, February 15, 2010 10:57AM - 11:09AM |
P8.00002: The Photoproduction of K$^{+}\Sigma^{\ast -}$(1385) Haiyun Lu, Ralf Gothe, Lewis Graham, Zhiwen Zhao, Kijun Park The $\Sigma $*(1385) resonance is a member of the baryon decuplet with spin 3/2. The cross section measurement for photoproduction helps to constrain the SU(3) model, as well as to test various other baryon models. There is very little photoproduction data on the neutron. So far, there exists only one published paper (in January 2009 by LEPS collaboration) which covers beam energy from 1.5 GeV to 2.4 GeV and limited angle. We analyze EG3 data from Hall B using CEBAF Large Acceptance Spectrometer(CLAS) in JLab from the threshold energy of the deuteron production to around 5.5 GeV. After careful study, we produce a very clean exclusive data sample of quasi-free photoproduction on the neutron. We present preliminary results of total cross section and differential cross section of K$^{+}\Sigma ^{\ast -}$, as well as the decay angle distribution. [Preview Abstract] |
Monday, February 15, 2010 11:09AM - 11:21AM |
P8.00003: First results on the electrocouplings of high lying N* states from N$\pi\pi$ electroproduction off protons with the CLAS detector Victor Mokeev, Volker Burkert We extended a phenomenological model [1], that was utilized for the evaluation of resonance transition helicity amplitudes from N$\pi\pi$ electroproduction cross section data at W $<$ 1.6 GeV and $Q^2$ $<$ 0.6 GeV$^2$, to provide larger kinematic coverage. A successful description of the CLAS data [2] on nine differential N$\pi\pi$ cross sections was achieved at W $<$ 1.8 GeV and $Q^2$ $<$ 1.5 GeV$^2$. The phenomenological analysis allowed us to isolate the resonant contribution and to determine electrocouplings for states with masses above 1.6 GeV. For the first time, results for the $S_{31}(1620)$, $S_{11}(1650)$, $F_{15}(1685)$, $D_{33}(1700)$, and $P_{13}(1720)$ states were obtained from the analysis of the p$\pi^+\pi^-$ exclusive channel. \\[4pt] [1] V. I. Mokeev et al., arXiv:0906.4081[hep-ex], accepted by PRC.\\[0pt] [2] M.~Ripani et al., CLAS Collaboration, Phys. Rev. Lett. {\bf 91}, 022002 (2003). [Preview Abstract] |
Monday, February 15, 2010 11:21AM - 11:33AM |
P8.00004: Exclusive Analysis of the $\vec{\gamma}\, n \rightarrow K^{^+} \vec{\Sigma}^{^-}$ Reaction at $E_{\gamma}$=1.1-2.3 GeV Edwin Munevar, Barry Berman Strangeness channels have been shown to be important for the experimental search for missing resonances. They are uniquely suited because they allow the possibility of determining several spin observables. A recent experiment performed at Jefferson Lab (g13 run period)~\cite{g13}, using a liquid deuterium target with linearly and circularly polarized tagged photon beams covering energies from threshold to 2.3 GeV, and using the CLAS detector, provides high-quality data (about 52 billion triggers) with good kinematic coverage and many experimental observables available for each reaction channel. We have analyzed these data to measure strangeness photoproduction on the neutron, in particular, for the $\vec{\gamma}\, n \rightarrow K^{^+} \vec{\Sigma}^{^-}$ reaction. A preliminary first exclusive measurement of the photon beam asymmetry for this reaction will be presented. [Preview Abstract] |
Monday, February 15, 2010 11:33AM - 11:45AM |
P8.00005: Search for Missing Resonances in $\gamma p\to K^+\Lambda$ using circularly polarized photons on longitudinally polarized target Liam Casey Focus in the search for missing baryon resonances has been directed toward the prospect of performing a full partial wave analysis using all single and double polarization observables across multiple decay channels. In particular, the possibility of resonances coupling strongly to decay channels with strangeness is encouraging. Double polarization data has been taken in Jefferson lab's CLAS detector using circularly polarized photons on a longitudinally polarized frozen-spin butanol target. Measurement of the double polarization observables $E$ (beam--target) and $L_x$ and $L_z$ (target-recoil) for the $\gamma p\to K^+\Lambda$ channel will be presented and compared with model predictions. [Preview Abstract] |
Monday, February 15, 2010 11:45AM - 11:57AM |
P8.00006: $K^{*0}(892)\Lambda$ \& $K^{+}\Sigma^{-}(1385)$ Photoproduction on the Deuteron Paul Mattione, Daniel Carman Measurement of the spectrum of excited baryons and their decay is an important part of the effort to understand the structure of the nucleon. Coupled-channel analyses of pion, eta, and kaon production reactions are capable of extracting more information on the excited hadron resonances than simply using a partial-wave analysis of each of the reactions individually. However, these analyses are currently limited due to the missing polarization observables in these reactions. This will result in improved quark model predictions of the large mass $N^{*}$ states, where wide resonances and insufficient data make it difficult to differentiate the states from the background. In this vein, the CLAS g13 experiment at Jefferson Lab collected 50 billion events on deuterium using circularly and linearly polarized photon beams. It\textquoteright{}s predicted that the s-channel production of the \textbf{$\gamma n\rightarrow K^{*0}(892)\Lambda$} and \textbf{$\gamma n\rightarrow K^{+}\Sigma^{-}(1385)$} reactions will couple non-negligibly to the decays of several of the excited $N^{*}$ states. These include the $N^{*}(1945)$, $N^{*}(2070)$, $N^{*}(2090)$ for \textbf{$K^{*0}(892)\Lambda$} production, and the $N^{*}(1980)$ and $N^{*}(2095)$ for \textbf{$K^{+}\Sigma^{-}(1385)$} production. With data from the CLAS g13 experiment, preliminary results from studies of the \textbf{$\gamma D\rightarrow K^{*0}(892)\Lambda(p)$} and \textbf{$\gamma D\rightarrow K^{+}\Sigma^{-}(1385)(p)$} reactions will be shown. [Preview Abstract] |
Monday, February 15, 2010 11:57AM - 12:09PM |
P8.00007: $\phi$(1020) Photoproduction on the Neutron Anna Micherdzinska, Barry Berman The mechanism of $\phi$ photoproduction on the nucleon is not yet well understood. In order to differentiate between the various mechanisms proposed for $\phi$ photoproduction, data for both differential cross sections and spin observables are needed. All existing experimental data come from $\phi$ photoproduction on the proton, and there is only one published result currently available using a linearly polarized photon beam. There are no experimental results at all for $\phi$ photoproduction on the neutron. Our high-statistics and large-kinematic-coverage g13 experiment, using the CLAS at Jefferson Lab, where both linearly and circularly polarized photons were incident on a deuterium target, can provide such data. We are analyzing these data to extract angular distributions for the $\gamma + n \rightarrow K^+ K^- + n$ reaction channel. An update on the analysis of these data will be presented. [Preview Abstract] |
Monday, February 15, 2010 12:09PM - 12:21PM |
P8.00008: Towards more precise parameters of the $a_1(1260)$ resonance Peter Lichard, Martin Vojik We explore the experimental data on the three-pion decay of the $\tau$ lepton and on the electron-positron annihilation into four pions in an effort to improve the knowledge about the $a_1(1260)$ resonance and their interactions. Our models of those two processes are based on the same main ingredients. These include the running-mass propagators of the $a_1$ and $\rho$ resonances and an effective two-component interaction Lagrangian among the $a_1$, $\rho$, and pion fields. The $a_1$ mass and width are obtained together with the Lagrangian mixing parameter from a common fit to several sets of data on both processes. [Preview Abstract] |
Monday, February 15, 2010 12:21PM - 12:33PM |
P8.00009: Factorization in Charged Meson Production Tanja Horn Tests of the factorization of hard and soft physics are of fundamental interest for our understanding of the dominant mechanism in exclusive reactions. Increasing the photon virtuality ($Q^2$) in electron scattering experiments allows one to become more and more sensitive to the partonic picture in which hard and soft physics have been shown to factorize. This is of particular importance for Generalized Parton Distributions (GPDs), which have been suggested to provide the most complete description of the non-perturbative physics. Meson electroproduction at intermediate energies provides a good way to study the transition from the non-perturbative to the perturbative regime. In this talk I will review tests of factorization of long- and short-distance physics in charged pion production, describe the connection to the pion form factor, and show extensions of these studies to the strange sector. [Preview Abstract] |
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