Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session J12: Hadronic Physics III |
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Sponsoring Units: GHP DNP Chair: Michael Kohl, Hampton University Room: A222-223 |
Sunday, April 15, 2018 1:30PM - 1:42PM |
J12.00001: Chiral Light Front Perturbation Theory and the Flavor Dependence of the Light-Quark Nucleon Sea Mary Alberg, Gerald A. Miller The light-quark flavor dependence of the proton sea has been of great interest for many years because of its close connection with non-perturbative effects. One hypothesis is that the sea arises from the pion cloud of the proton. We make precise predictions, based on the pion cloud idea, for the anticipated final results of the SeaQuest experiment. This is achieved by applying light cone perturbation theory and experimental constraints to a chiral Lagrangian so that the relevant Fock-space components of the nucleon wave function are computed with reasonable accuracy. We compare our results to existing experimental information from E866 regarding the light flavor sea, and make predictions, including uncertainties, for future experimental measurements. Future experimental results will either confirm or rule out the idea that the pion cloud provides the flavor dependence of the proton's sea quark distributions, and have profound implications for understanding the nucleon-nucleon force. [Preview Abstract] |
Sunday, April 15, 2018 1:42PM - 1:54PM |
J12.00002: Lattice Parton Distribution Functions at Physical Pion Mass Huey-Wen Lin We present the first lattice results on isovector unpolarized, longitudinally and transversely polarized parton distribution functions (PDFs) at physical pion mass. The PDFs are obtained using the large-momentum effective field theory (LaMET) framework where the full Bjorken-$x$ dependence of finite-momentum PDFs, called ``quasi-PDFs'', can be calculated on the lattice. The quasi-PDF nucleon matrix elements are renormalized nonperturbatively in RI/MOM-scheme. We demonstrate the current state-of-the-art of the 2+1+1-flavor lattice data at physical pion mass with lattice spacing 0.09~fm and volume $(5.76\mbox{ fm})^3$. [Preview Abstract] |
Sunday, April 15, 2018 1:54PM - 2:06PM |
J12.00003: Nucleon structure functions at large Bjorken x from 12 GeV commissioning experiment E12-10-002 in Hall C Debaditya Biswas, Abel Sun Extractions of $\rm F_{2}$ structure function from inclusive inelastic electron-proton scattering cross sections is important for the study of nucleon structure. Most existing data have large statistical uncertainties in the region of large Bjorken $x$. After the successful 12 GeV upgrade of Jefferson Lab, E12-10-002 is one of the first commissioning experiments ran in Hall C to measure the inclusive inelastic electron-proton scattering cross sections in the $\rm Q^{2} $ region of 4 to 14 $\rm GeV^{2}$. In this talk an overview of experiment E12-10-002 will be presented. [Preview Abstract] |
Sunday, April 15, 2018 2:06PM - 2:18PM |
J12.00004: Measurement of the $\frac{F_2^n}{F_2^p}$ ratio in the JLab MARATHON experiment Michael Nycz The $\frac{F_2^n}{F_2^p}$ structure function ratio has been measured previously from Deep Inelastic Scattering, using proton and deuterium targets to extract the $F_2^p$ $F_2^n$ structure functions respectively as well as the$\frac{d}{u}$ quark distribution function ratio. The lack of a free neutron target has made the extraction of $F_2^n$ challenging due to nuclear corrections, which result in large uncertainties in the $\frac{F_2^n}{F_2^p}$ and $\frac{d}{u}$ quark distribution function in the high x region. Likewise, various theory predictions based on SU(6) symmetry, pQCD, and the diquark model make different predictions for both ratios in the limit x $\rightarrow$ 1, all of which fit within the present uncertainty of $\frac{F_2^n}{F_2^p}$ at large x. To avoid the issues related with extracting $F_2^n$, MARATHON, a experiment currently running in Hall A at Jefferson Lab, used $^3He$ and $^3H$, to extract $\frac{F_2^n}{F_2^p}$ and thus $\frac{d}{u}$ by exploiting the isospin symmetry of the A=3 mirror nuclei. This will result in the determination of the $\frac{F_2^n}{F_2^p}$ and $\frac{d}{u}$ ratios with minimal theoretical uncertainties. This work is supported by NSF Grants PHY-1405814 and PHY-1714809 (Kent State University), and DOE Contract DE-AC05-06OR23177 (JLab) [Preview Abstract] |
Sunday, April 15, 2018 2:18PM - 2:30PM |
J12.00005: Status of the Jefferson Lab Marathon Experiment Tong Su MARATHON experiment (E12-010-103) at Hall A of Jefferson Lab (JLab) will perform precise measurements of the deep inelastic cross section ratio for scattering from the 3H and 3He mirror nuclei, in the Bjorken x kinematic range of x = 0.22 to x = 0.82. These measurements will result in the extraction of the neutron to proton structure function $F_{2}^{n}/F_{2}^{p}$ ratio, and the ratio $d/u$ quark distributions in the proton with minimal theoretical uncertainties. The experiment will also provide precise data on the EMC effect for both A=3 nuclear systems. The experiment is in progress. In this presentation, a brief introduction and the status of the experiment will be presented. This work is supported by NSF Grants PHY-1405814 and PHY-1714809 (Kent State University), and DOE Contract DE-AC05-06OR23177 (JLab). [Preview Abstract] |
Sunday, April 15, 2018 2:30PM - 2:42PM |
J12.00006: Light unflavored mesons in a light-front Hamiltonian approach Wenyang Qian, Shaoyang Jia, Yang Li, James Vary We study the light unflavored mesons as relativistic bound states of a valence quark and anti-quark pair in the effective Hamiltonian framework of the Basis Light-Front Quantization (BLFQ) approach. The light-front holography and one-gluon exchange effective Hamiltonian [Phys. Rev. D 96, 016022] is supplemented with a pseudoscaler interaction term such that effects of dynamical chiral symmetry breaking on the pion valence quarks are simulated. The effective Hamiltonian is then diagonalized to obtain the meson light-front wave functions for the valence quarks. In this model, we present the mass spectroscopy, decay constants, the r.m.s. radii, and the parton distribution amplitudes calculated from the valence wave functions. This formalism serves as an initial step in our investigation of the light meson phenomenology. [Preview Abstract] |
Sunday, April 15, 2018 2:42PM - 2:54PM |
J12.00007: Baryons in a light-front approach Anji Yu We present a model for baryons based on light-front holography. The effective 3-body Hamiltonian consists of a transverse confining interaction based on the AdS/QCD soft-wall model and a longitudinal confining interaction recently applied to the meson system [1]. We analyze the mass spectrum of nucleons and use the obtained ground-state wave functions to calculate observables such as the electromagnetic form factor and the charge radius. We also compare the model results with experiments and results of holographic QCD. [1] Y. Li, P. Maris, and J.P. Vary, Phys. Rev. DÂ \textbf{96}, 016022 (2017); arXiv:1704.06968 [Preview Abstract] |
Sunday, April 15, 2018 2:54PM - 3:06PM |
J12.00008: A measurement of the Compton scattering cross section during the PrimEx-II experiment at JLab Li Ye The electron Compton scattering is the best known fundamental QED process, however, a precision measurement of its cross section for the beam energy above 1 GeV has been lacking up to now. An updated high precision measurement of the neutral pion lifetime via the Primakoff effect (PrimEx-II) experiment was performed in Hall B of Jefferson Lab in 2010. The experiment used small angle coherent photoproduction of $\pi^0$'s in the Coulomb field of a nucleus, $i.e.$ the Primakoff effet, to determin the lifetime with a precision of better than $1.5\%$ . It therefore requires thorough understanding of the underlying systematic uncertainties. To facilitate that data for well known electromagnetic processes were taken concurrently with the photoproduction data. We will present an analysis that pertains to measuring the Compton scattering cross section, which occurs at similar kinematics as the primary process. The combination of the well established theory of this process with large collected statistics allowed to extract this cross section with high precision in an energy region of 4-5 GeV for $^{12}C$ and $^{28}Si$ targets. The results of this analysis will be presented. [Preview Abstract] |
Sunday, April 15, 2018 3:06PM - 3:18PM |
J12.00009: Commissioning the Super High Momentum Spectrometer in Hall C at Jefferson Lab Holly Szumila-Vance The Super High Momentum Spectrometer (SHMS) is a new spectrometer installed in Hall C at Jefferson Lab that can detect particles over a range of central momenta from 2--11~GeV/c and scattering angles from 5.5 to 40 degrees. Jefferson Lab delivers a high intensity electron beam with an energy up to 11~GeV to fixed targets in Hall C. The SHMS is a highly precise and essential upgrade for the 12~GeV Jefferson Lab physics program. Its beam line consists of a dipole magnet with a 3-degree horizontal bend, three quadrupole magnets for horizontal and vertical focusing of the beam, and the spectrometer dipole capable of a 4~T central magnetic field and 18.4-degree bend angle. Measurements in Hall C can be taken with the SHMS independently or in coincidence with the existing High Momentum Spectrometer (HMS). The SHMS was installed in the spring of 2017 and commissioned during the fall 2017/winter 2018 using a range of electron beam energies. This talk summarizes the initial results of the optics tuning of the SHMS and the performance during recent experimental running to include initial elastic hydrogen scattering measurements. [Preview Abstract] |
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