Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session X8: Hadronic Physics IV |
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Sponsoring Units: DNP Chair: Liguang Tang, Hampton University/Thomas Jefferson National Accelerator Facility Room: Delaware B |
Tuesday, February 16, 2010 10:45AM - 10:57AM |
X8.00001: Branching Ration of the radiative decay of the Sigma+(1385) Dustin Keller The CLAS g11 data set with proton target is used to extract measurements of the radiative decay $\Sigma^{*+} \to \Sigma^+\gamma$ using neutron detection. Though neutron detection is not standard in CLAS, neutral particles can be identified as clusters in the Electromagnetic Calorimeter that are not associated with any charged track reconstructed in the drift chambers. In the identification scheme used photons are neutral hits with a $\beta$ $>$ 0.9 while neutrons are hits with $\beta$ $<$ 0.9. Once the momentum and position resolution is understood for neutrons they can be used in kinematic fitting along with the other charged particles to obtain a missing mass dependent on the topological requirement. Decays of the $\Sigma^{*+}$ that include a $\pi^{0} \to \gamma+\gamma$ easily overwhelm the radiative decay signal so care is taken to reduce this background with kinematic constraints. First world data on a branching ratio for the radiative channel is presented. [Preview Abstract] |
Tuesday, February 16, 2010 10:57AM - 11:09AM |
X8.00002: Data Analysis Strategy for Spectroscopic investigation of Lambda hypernuclei in the wide mass region using the (e,e'K) reaction Zhihong Ye The third-generation hypernuclear experiment in Hall C Jefferson Lab, \emph{E05-115}, has successfully finished data taking at the end of October 2009. To obtain high resolution hypernuclei missing mass spectra, a precise optics tuning is crucial to describe properties of two complete new spectroscopes, HKS for Kaon, HES for Electron, as well as a new splitter magnet for \emph{(e',K)} separation, particle identification for Kaon will help us to get hypernuclei spectra with good S/N ratio and sufficient yield, specially for $^{51}$$_{\Lambda}$V, which is the first heavy hypernuclear we investigate, and kinematic calibration is also very important to give correct and precise sub-structure of hypernuclear states. I will briefly discuss our analysis procedure and show some preliminary results. [Preview Abstract] |
Tuesday, February 16, 2010 11:09AM - 11:21AM |
X8.00003: Overview for Spectroscopic estigation of Lambda hypernuclei in the wide mass region using the (e,e'K) reaction Chunhua Chen The third-generation hypernuclear experiment in Hall C Jefferson Lab,\emph{E05-115},has successfully finished data taking at the end of October 2009.The HKS-HES experiment aims to obtain high resolution hypernuclear spectroscopy from light to heavy mass region using the (\emph{e,e'K$^{+}$}) reaction.The HKS spectrometer system used as kaon arm in 2005 \emph{E01-011} experiment gave us a large kinematics coverage which allows the experiment to obtain high precision information about the absolute binding energy of the hypernuclear ground states,in addition to the excitation energy of the hypernuclear excited states. The HES spectrometer system for electrom arm and a new splitter are used in Hall C to explore hypernuclei in wide mass region (upto \emph{A=89}), and investiagte high excitation states upto \emph{d} shell with the resolution as best as \emph{400 KeV}. [Preview Abstract] |
Tuesday, February 16, 2010 11:21AM - 11:33AM |
X8.00004: Coulomb Sum Rule at 0.55 GeV/$c$ $\leq \vec {\vert q \vert} \leq$ 1.0 GeV/$c$ Huan Yao In order to test the Coulomb sum rule in nuclei, a precision measurement of inclusive electron scattering cross sections in the quasi-elastic region was performed at Jefferson Lab. Incident electrons of energies ranging from 0.4 GeV/$c$ to 4 GeV/$c$ scattered off $^{4}$He, $^{12}$C, $^{56}$Fe and $^{208}$Pb nuclei at four scattering angles ( $15\,^{\circ}$, $60\,^{\circ}$, $90\,^{\circ}$, $120\,^{\circ}$ ) and scattered energies ranging from 0.1 GeV/c to 4 GeV/c. The Rosenbluth method is used to extract the transverse and longitudinal response functions at three-momentum transfers 0.55 GeV/$c$ $\leq \vec {\vert q \vert} \leq$ 1.0 GeV/$c$. Proper Coulomb corrections will be applied. The Coulomb Sum will be determined in the above $\vec {\vert q \vert} $ range and compared to predictions. Progress of data analysis will be presented. [Preview Abstract] |
Tuesday, February 16, 2010 11:33AM - 11:45AM |
X8.00005: Latest results from Jefferson Lab HKS experiment Lulin Yuan The goal of Jefferson Lab HKS experiment is to obtain high resolution spectroscopy for $^{12}_\Lambda$B, $^{28}_\Lambda$Al and $^{7}_\Lambda$He hypernuclei. Recently, to further improve the precision of the binding energy determination, we have done a thorough new analysis with better tracking resolution at spectrometer focal planes and a new kinematics calibration procedure. In this talk, I will present the latest spectra of $^{12}_\Lambda$B, $^{28}_\Lambda$Al and $^{7}_\Lambda$He and compare them to the most recent theoretical predictions. [Preview Abstract] |
Tuesday, February 16, 2010 11:45AM - 11:57AM |
X8.00006: The $\pi^0$ Lifetime: Experimental Probe of the QCD Chiral Anomaly Dustin McNulty The $\pi^0 \rightarrow \gamma\gamma$ decay rate is a fundamental prediction of QCD which gives insight into one of its most profound symmetry issues---namely, the Chiral Anomaly. It is this anomalous symmetry-breaking mechanism by which the $\pi^0 \rightarrow \gamma\gamma$ decay channel primarily proceeds, and thus a measure of its rate or partial width, $\Gamma_{\gamma\gamma}$, represents a direct probe of the anomaly plus chiral corrections. The PrimEx Collaboration at Jefferson Lab has extracted $\Gamma_{\gamma\gamma}$ from precision measurements of $\pi^0$ photo-production cross sections using their Primakoff components. Measurements were made using $5 \%$ X$_{\mathrm{o}}$ nuclear targets of $^{12}\mathrm{C}$ and $^{208}\mathrm{Pb}$ with incident photons between $4.9$ and $5.5\mathrm{GeV}$ tagged by the Hall B tagger facility. The $\pi^0$ decay photons were detected at very forward angles by a specially constructed high resolution hybrid calorimeter (HyCal). In this presentation, the final result from the PrimEx measurement will be given along with a general overview of the physics, experimental setup, and data analysis strategies and techniques. [Preview Abstract] |
Tuesday, February 16, 2010 11:57AM - 12:09PM |
X8.00007: Partial decay widths of negative parity baryons in the 1/Nc expansion Chandana Jayalath, Jose Goity, Norberto Scoccola The partial decay widths of negative parity excited baryons into pseudo-scalar mesons are studied in the framework of the 1/Nc expansion of QCD to order 1/Nc, and to first order in SU(3) symmetry breaking by the quark masses. In particular, the S and D wave decays of excited baryons in 70-plet of spin-flavor SU(6) are analyzed using the empirical partial decay widths from the Particle Data Group. The importance of two-body effects in the decay amplitudes can be elucidated. Several parameter free relations between partial decay widths are found and tested. The consistency of state-mixing as obtained from the analysis of the decays and from the analysis of the masses is addressed. [Preview Abstract] |
Tuesday, February 16, 2010 12:09PM - 12:21PM |
X8.00008: A Study of Boundary Conditions in Background Field Simulations in Lattice QCD Scott Moerschbacher, Frank Lee, Andrei Alexandru We investigate the effect of boundary conditions on magnetic fields in lattice QCD simulations of hadron two-point correlation functions using the background field method. This is a controlled study in which two sets of calculations are carried out with only the boundary conditions being varied - all other properties such as the magnetic field strength, pion mass, and lattice spacing are held fixed. The first set uses Dirichlet boundary conditions with the source placed in the center of the lattice, far away from the boundary in order to minimize effects from the derivative discontinuity at the boundary. The other method produces a constant field everywhere on the lattice by adding transverse links, so-called ``patching'' the field. This approach stresses the more physical constraint that the magnetic flux through the boundary should be continuous. We find deviations in the two correlators on the order of a few percent or less. Finally, we demonstrate this effect by calculating magnetic moments and polarizabilities of selected hadrons within both frameworks. [Preview Abstract] |
Tuesday, February 16, 2010 12:21PM - 12:33PM |
X8.00009: Magnetic Moments of Negative-Parity Baryons from Lattice QCD Frank Lee, Aryan Khojandi, Andrei Alexandru Using the background field method, we compute the magnetic moments for the entire family of negative-parity octet and decuplet baryons. They are extracted from small mass shifts caused by external magnetic fields introduced on the lattice. The calculations are done on quenched configurations using standard Wilson actions, six pion masses down to about 500 MeV, and four field strengths. High statistics (we use 1500 configurations) are needed to isolate the signal for these particles. For comparison purposes, we also extract the magnetic moments for the positive-parity counterparts. [Preview Abstract] |
Tuesday, February 16, 2010 12:33PM - 12:45PM |
X8.00010: MathQCDSR: a Mathematica Package for QCD Sum Rules Calculations Lai Wang, Frank X. Lee We present a software package written in Mathematica for standard QCD sum rules calculations. Two examples are given to demonstrate how to use the package. One is for the mass spectrum of octet baryons from two-point correlation functions; the other for the magnetic moments of octet baryons in the external-field method. The software package FeynCalc is used to handle the gamma-matrix computations. The derived sum rules can be saved in various forms (native Mathematica, JAVA, Fortran, or Latex). Several notebooks are provided to carry out a Monte-Carlo-based numerical analysis of the sum rules, complete with in-line graphical display of sum rule matching, error distributions, scatter plots for correlations, etc. [Preview Abstract] |
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