Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session KC: Hadron and Hypernuclear Spectroscopy |
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Chair: Pawel Nadel-Turonski, Thomas Jefferson National Accelerator Facility Room: Grand Ballroom III |
Friday, October 25, 2013 2:00PM - 2:12PM |
KC.00001: Search for Exotic Mesons in $\gamma p\rightarrow\Delta^{++}\pi^{+}\pi^{-}\pi^{-}$ with CLAS at Jefferson Lab Aristeidis Tsaris Apart from the mesons that the constituent quark model predicts, QCD allows for additional states beyond the $q\bar{q}$ system. By studying the following reaction $\gamma p\rightarrow\Delta^{++}\pi^{+}\pi^{-}\pi^{-}$ we are analyzing a large data set of three charged pion system. An event selection has been made to this data set in order to search for the spin-parity exotic $\pi_{1}(1600)$ meson. Those events will be subject to PWA in search for this exotic meson. The experiment took place at Jefferson Lab using the CLAS spectrometer, a liquid hydrogen target was used and a tagged photon beam in a range of $4.4-5.5$ GeV. Preliminary results will be shown, describing the data quality, kinematics and Monte Carlo simulation of the reaction. [Preview Abstract] |
Friday, October 25, 2013 2:12PM - 2:24PM |
KC.00002: Photoproduction of scalar mesons at CLAS Shloka Chandavar, Kenneth Hicks, Dennis Weygand A single gluon, which carries color charge, cannot exist independently outside a hadron. Lattice QCD calculations in pure SU(3), however, predict the existence of glueballs which are bound states of two or more gluons. In the real world, the challenge to identify glueballs experimentally is the fact they mix with meson states. The $f_{0} (1500)$ is one of several candidates for the lightest glueball, with $J^{PC}=0^{++}$. We investigate the presence of this particle in photoproduction by analyzing the reaction $\gamma p\to f_{J} p\to K_{S}^{0} K_{S}^{0} p\to 2(\pi^{+}\pi^{-})p$. This reaction was studied using data from the g12 experiment performed using the CLAS detector at Jefferson Lab. A preliminary partial wave analysis, performed on the $K_{S}^{0} K_{S}^{0} $ invariant mass spectrum, will be presented. These results update those presented for this reaction channel at previous conferences. [Preview Abstract] |
Friday, October 25, 2013 2:24PM - 2:36PM |
KC.00003: The Photoproduction of Strangeness in $\gamma p \rightarrow \Lambda K^{+} \pi^{+} \pi^{-}$ with CLAS at Jefferson Lab Hussein Ghoul Following the prediction of exotic states by Quantum Chromodynamics, the search for new and exotic mesons has become a priority in nuclear physics. The g12 Experiment, using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab, has provided a large photoproduction dataset. This experiment used a liquid hydrogen target, a 4 - 5.5 GeV tagged photon beam, and acquired 26 billion events. The reaction $\gamma p \rightarrow \Lambda K^{+} \pi^{+} \pi^{-}$ provides an opportunity for searching for excited strange mesons, in the $K^{+} \pi^{+} \pi^{-}$ system, using the g12 dataset. In this reaction, the $\Lambda$ is identified via the p $\pi^{-}$ decay. Studies indicate two dominating decay modes: the $K^{*}(982) \pi$ mode, and the $K^{+}\rho$ mode. Preliminary results will be presented in this talk, along with the kinematics and dynamics of this reaction. Future plans, including partial wave analysis of the dataset, will be discussed briefly. [Preview Abstract] |
Friday, October 25, 2013 2:36PM - 2:48PM |
KC.00004: Baryon Antibaryon Photoproduction using CLAS at Jefferson Lab William Phelps There is little known about the baryon antibaryon production mechanism. The following reactions were looked at, $\gamma$p$\rightarrow$pp$\bar{p}$, $\gamma$p$\rightarrow$pp$\pi^{-}\bar{n}$, and $\gamma$p$\rightarrow$p$\bar{p}\pi^{+}$n. For these reactions the photon energies that were selected were from 4.4-5.45 GeV. The data were from the g12 experiment taken with the CLAS detector using a liquid hydrogen target at Thomas Jefferson National Accelerator Facility. This experiment had high statistics, with a luminosity of 68 pb$^{-1}$. Features of the data such as invariant mass spectra, missing mass spectra, and angular distributions necessary for the analysis will be shown. In addition, a first observation of antineutrons in photoproduction in the missing mass spectra of $\gamma$p$\rightarrow$pp$\pi^{-}\bar{n}$ will also be shown. [Preview Abstract] |
Friday, October 25, 2013 2:48PM - 3:00PM |
KC.00005: Observation of Scaling in the Ratio of Electroproduction Yields of Three Meson-Baryon Final States: $K^+\Lambda$, $n\pi^+$, $p\pi^0$ Mac Mestayer, Kijun Park We measured the ratios of electroproduction cross-sections for three exclusive meson-baryon final states: $K^+\Lambda$, $p\pi^0$, and $n\pi^+$. After averaging over the angle between leptonic and hadronic production planes we observe only a moderate kinematic dependence (``scaling'') of the ratios with respect to $Q^2$, $W$ and $\cos\theta^{*}$. Our results agree well with a simple calculation based on the ``Lund model'' for hadronization in which the color flux-tube is broken by the creation of $q\overline{q}$ pairs and which works well up to center-of-mass energies equal to the $Z^0$ mass. Interestingly, our measured global average $K^+\Lambda$$/$$n\pi^+$ production ratio of $0.278 \pm 0.013 \pm 0.042$ agrees with the nominal value of the ``strangeness suppression factor'' of the Lund model of $0.3$; extending the universality of this concept to the exclusive limit in which only a single $q\overline{q}$ pair is created and for which an explict two-body phase-space correction can be performed. In addition, our measurement of the $p\pi^0$$/$$n\pi^+$ ratio of $0.467 \pm 0.008 \pm 0.086$ is consistent with equality of the $u\overline{u}$ and $d\overline{d}$ pair creation probabilities. [Preview Abstract] |
Friday, October 25, 2013 3:00PM - 3:12PM |
KC.00006: Fermilab Experiment-906/SeaQuest: Exploring Nucleon Structure through the Drell-Yan Process Bryan Ramson SeaQuest will investigate the large light-flavor asymmetry in the nucleon sea first experimentally observed by the CERN New Muon Collaboration (NMC) and further investigated by Fermilab Experiment-866/NuSea. Through the Drell-Yan process produced in collisions between 120 GeV protons provided by the Fermilab Main Injector and fixed hydrogen and deuterium targets, SeaQuest will measure the ratio of $\bar{d}(x_{t})$ and $\bar{u}(x_{t})$ at momentum fractions in the interval $0.11 \le x_{t} \le 0.45$. At this beam energy, Drell-Yan production is enhanced roughly by a factor of seven while background J/$\psi$ production is reduced by the same factor relative to the rates of NuSea's 800 GeV beam. This leads to an enhanced precision by roughly a factor of 50. Additionally, the lower center-of-mass energy and higher precision of the SeaQuest experiment will allow for an enhanced investigation of parton energy loss through cold nuclear matter and significantly improve measurement of the modification of sea quark densities in the nuclear environment. SeaQuest had an initial two month commissioning run in March and April of 2012. Results from the commissioning run and an update on the recently undertaken two year second run will be presented. [Preview Abstract] |
Friday, October 25, 2013 3:12PM - 3:24PM |
KC.00007: New Data Analysis for Hypernuclear Spectroscopy Experiment E01-011 at Jefferson Laboratory Hall C Yuncheng Han The E01-011 experiment was performed at JLab Hall-C by (e, e'K$^{+}$) reaction in 2005 to investigate hypernuclear structures, concentrating on spectroscopy of $^{7}_{\Lambda}He$, $^{12}_{\Lambda}B$, and $^{28}_{\Lambda}Al$. The result of $^{7}_{\Lambda}He$ has already been published. However, the following 2009 experiment demonstrated issues may affect the accuracy of the $^{28}_{\Lambda}Al$ spectroscopy, considering that the previous analysis separated the kinematics space into two regions and allowed applying independent optical matrices. It is necessary to make a verification of $^{28}_{\Lambda}Al$ spectrum with a more reliable analysis to ensure its correctness. The new analysis started with an investigation on the asymmetry of the spectrometer magnetic fields and then followed by mathematical optimization (MINUIT) for the magnetic optics using the calibration events with known masses. The results from the new analysis will be presented in this talk. [Preview Abstract] |
Friday, October 25, 2013 3:24PM - 3:36PM |
KC.00008: Recent Spectroscopic Investigation of P-Shell $\Lambda$-Hypernuclei by the (e, e'K$^{+}$) Reaction Chunhua Chen Hypernuclei is a unique laboratory to study YN interaction. P-shell $\Lambda$-hypernuclei has its advantage to study both the fine structure and cluster structure of hypernuclei. The third-generation (\emph{e,e'K$^{+}$}) hypernuclear experiment E05115 at JLAB HallC was carried out in 2009. The goal of the experiment is to obtain high precision spectroscopy in wide mass range. The experimental system especially the optics and the kinematics have been carefully studied. The updated calibraion status and the p-shell spectroscopy of $^{12}_\Lambda$B, $^{7}_\Lambda$He, and $^{10}_\Lambda$Be will be discussed in this talk. [Preview Abstract] |
Friday, October 25, 2013 3:36PM - 3:48PM |
KC.00009: Cascade hyperon production in anti-kaon- and photon-induced reactions Benjamin Jackson, Kanzo Nakayama In preparation for the forthcoming experiments on multi-strangeness baryon production at JLab and J-PARC, we analyze the general features of cascade production in both the anti-kaon- and photon-induced reactions. Particular attention is paid to the spin structure of the reaction amplitude for producing cascade resonances with the emphasis on identifying the spin observables required to determine the production amplitude as well as the spin-parity of the resonance. For the production of cascade resonances with spin higher than 1/2, the spin-density-matrix formalism is proven to be particularly useful. The $\gamma N \to K K \Xi$ and $\bar{K}N \to K \Xi$ reactions are investigated within a simple model. [Preview Abstract] |
Friday, October 25, 2013 3:48PM - 4:00PM |
KC.00010: Search for the five-quark components in the ground-state baryons Bijan Saghai, C.S. An Sea quark contents of the octet baryons are investigated by employing an extended chiral constituent quark approach, which embodies higher Fock five-quark components in the baryons wave-functions. We calculate both diagonal and non-diagonal matrix elements for all 17 five-quark configurations and remove contributions from the center-of-mass motion of the quark clusters. Results are compared to other theoretical findings, such as lattice-QCD, and to various data coming from JLab, Fermi Lab, MAMI... on the observables such as strangeness magnetic form factor of the proton, flavor asymmetry of the nucleon sea $\bar{d}-\bar{u}$, radiative and strong decays of the $\Lambda(1405)$ resonance, strong decay of low-lying $S_{11}$ and $D_{13}$ nucleon resonances... Probabilities of $\bar{u}$, $\bar{d}$ and $\bar{s}$ in the nucleon, $\Lambda$, $\Sigma$ and $\Xi$ baryons, due to the intrinsic five-quark components in the baryons wave functions are predicted, based on the probability amplitudes calculated within the most commonly accepted $q\bar{q}$ pair creation mechanism, namely, the $^{3}P_{0}$ model. [Preview Abstract] |
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