Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session B12: Hadronic Physics I |
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Sponsoring Units: GHP DNP Chair: Ian Cloet, ANL Room: A222-223 |
Saturday, April 14, 2018 10:45AM - 10:57AM |
B12.00001: Calculations of the Parton Structure of the Nucleon* Kyle Bednar, Ian Cloet, Peter Tandy The quark parton structure of the nucleon is calculated in an approach based upon QCD's Dyson-Schwinger equations. The method accommodates a variety of QCD’s dynamical outcomes including the running mass of quark propagators and the formation of non-pointlike diquark correlations. The integral elements, including the nucleon amplitude from a previous solution of the Poincar\'e covariant Faddeev equation, are those which have been successful in describing elastic nucleon form factors. The presented spin-independent PDFs are in good agreement with experiment. The relative importance of scalar and axial-vector diquark correlations will be explored. Preliminary results for spin-dependent PDFs and TMDs will be presented if available. [Preview Abstract] |
Saturday, April 14, 2018 10:57AM - 11:09AM |
B12.00002: The search for color transparency through the A(e, e$^\prime$p) reaction at 12 GeV Md Latiful Kabir The suppression of the final-state interactions of a hadron propagating through the nuclear medium at high momentum transfer is known as the color transparency (CT) and is a robust prediction of QCD. The onset of CT is of extreme interest in hadronic physics. For example, the onset of CT is related to the onset of factorization, which is an important requirement for accessing GPDs in deep exclusive meson production. The onset of CT has been observed in mesons, but is unconfirmed for baryons. However an enhancement in the transparency was observed in A(p, 2p) reactions at BNL. The E12-06-107 experiment in Hall-C seeks to measure the proton transparency up to the highest $Q^2$ achievable using the 12-GeV beam at the Jefferson Lab. The experiment uses SHMS-HMS spectrometer pair to perform the coincidence measurement from the reaction A(e, e$^\prime$p). The proton momentum range covered in the experiment overlaps with the region where the enhancement was observed at BNL, and hence this experiment will help verify the origins of the enhancement and at the same time search for the onset of CT for protons. I will talk about the current status of the experiment. [Preview Abstract] |
Saturday, April 14, 2018 11:09AM - 11:21AM |
B12.00003: Form Factors and Generalized Parton Distributions of Heavy Quarkonia in Basis Light Front Quantization Lekha Adhikari, Yang Li, Meijian Li, Pieter Maris, James P. Vary We calculate the electromagnetic (charge, magnetic and quadrupole) form factors and associated quantities, charge radii, magnetic moments, and quadrupole moments of heavy quarkonia (charmonia and bottomonia) using the Basis Light Front Quantization (BLFQ). For this work, we adopt light front wave functions (LFWFs) generated by the holographic QCD confining potential and the one-gluon exchange interaction with a fixed coupling. Using the same LFWFs generated in the BLFQ, we also present the generalized parton distributions (GPDs) for selected quarkonia including those for radially excited mesons such as $\psi$ and $\Upsilon^\prime$. [Preview Abstract] |
Saturday, April 14, 2018 11:21AM - 11:33AM |
B12.00004: Measuring the Neutron Magnetic Form Factor to High-$Q^2$ Using the Ratio Method and the New Super BigBite Spectrometer Juan Carlos Cornejo Few measurements of the Neutron Magnetic Form Factor ($G^n_M$) exist at high-$Q^2$ and these have large systematic uncertainties. These uncertainties can be significantly reduced by using the Ratio Method in which a ratio of the quasi-elastic electron-neutron and electron-proton scattering from a deuterium target is used to extract $G^n_M$. The GMn experiment will use the Ratio Method to measure $G^n_M$ for a $Q^2$ of 3.5 to 13.5 $(GeV/c)^2$ with high precision. This experiment will be the first to use the new large-aperture spectrometer being built as part of the SBS program in Hall A at Jefferson Lab. The spectrometer will be used to vertically separate the protons and neutrons, which will then be detected by a new hadron calorimeter. The scattered neutrons and protons will be detected in coincidence with electrons scattered into the existing BigBite spectrometer. In this talk I will discuss the experiment and specifics of how we intend to minimize the systematic uncertainties. [Preview Abstract] |
Saturday, April 14, 2018 11:33AM - 11:45AM |
B12.00005: Precision Measurement of the Proton Elastic Cross-Section at High $\rm Q^{2}$ Thir Gautam, Bashar Aljawrneh, Barak Schmookler, Longwu Ou, Yang Wang Elastic electromagnetic form factors characterize the distribution of electric charge and magnetization current inside the nucleon and thus reflect the internal structure determined by Quantum Chromodynamics. Existing data on the proton magnetic form factor at high $\rm Q^{2}$ have large statistical and systematic uncertainties. The GMp experiment E12-07-108 was one of the first set of experiments to run in Hall A at Jefferson Lab after the 12 $\rm GeV$ upgrade with the goal to precisely measure the electron-proton elastic cross section in the $\rm Q^{2}$ range of 7 to 17 $\rm GeV^{2}$ with an accuracy of better than 2% - several times better than existing data at this $\rm Q^{2}$ range. This will allow further tests of form factor scaling predicted by pQCD and, additionally, will be an important benchmark for many other experiments where elastic electron-proton scattering is used for normalization. The new 12 GeV beamline in Hall A, with main instrumentation consisting of beam charge and position monitors, was commissioned during the Fall of 2016. In addition, production data at energies 2,4,6,8 and 11 GeV were taken. In this talk, the preliminary results of cross-section study within 3% will be presented. [Preview Abstract] |
Saturday, April 14, 2018 11:45AM - 11:57AM |
B12.00006: Asymmetry Measurement of the Electric Form Factor of the Neutron Richard Obrecht The space-like electric form factor of the neutron has been extracted at $Q^2=1.16$ GeV$^2$ via a beam-target helicity asymmetry measurement using the semi-exclusive reaction $^3\vec{\textrm{He}}(\vec{e},e'n)pp$. The Jefferson Lab Hall A experiment E02-013 ran in 2006 utilizing the 6 GeV CEBAF for its high-duty, longitudinally polarized electron beam. The double-arm coincidence experiment detected the quasielastically scattered electrons in a large angular and momentum acceptance spectrometer referred to as BigBite. The recoiling nucleons were detected in a large neutron detector, built out of planes of scintillator arrays interlaced with iron and lead plates to increase the probability of inducing a hadronic shower. The polarized $^3$He target used the novel technique of hybrid spin-exchange optical pumping, resulting in a 10 atm target that could sustain polarizations greater than 50$\%$ at a beam current of 8 $\mu$A. Presented will be the current analysis and a preliminary result for $G_E^n$ at $Q^2$=1.16 GeV$^2$. [Preview Abstract] |
Saturday, April 14, 2018 11:57AM - 12:09PM |
B12.00007: The Slope of the Nucleon Electromagnetic Form Factors from Coordinate-Space Moments of Matrix Elements. David Richards, Chris Bouchard, Chia Chang, Kostas Orginos The charge radius of the nucleon can be related to the slope of the electromagnetic form factors at zero momentum transfer. Calculations of the form factors using lattice QCD are typically obtained for a discrete set of momenta $Q^2$, from which the charge radius can be inferred. We present a method to compute the slope of electromagnetic form factors directly, including at $Q^2 = 0$, by computing the coordinate-space moments of current matrix elements. We begin by describing the formalism, which we then apply to the calculation of the isovector form factor of the nucleon. In particular, we examine the dependence of our results on the volume of the box in which the calculation is performed, thereby controlling one of the principle systematic uncertainties in the method. We conclude by proposing other applications of the technique. [Preview Abstract] |
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