Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session EM: Hadrons: Low-x physics |
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Chair: Simonetta Liuti, The University Of Virginia |
Friday, October 30, 2020 10:30AM - 10:42AM |
EM.00001: Probing nucleon strange and charm distributions with lattice QCD Rui Zhang, Huey-Wen Lin, Boram Yoon We present the first lattice-QCD calculation of the unpolarized strange and charm parton distribution functions using large-momentum effective theory (LaMET). We use a lattice ensemble with 2+1+1 flavors of highly improved staggered quarks (HISQ) generated by MILC collaboration, with lattice spacing $a\approx 0.12$~fm and $M_\pi \approx 310$~MeV, and clover valence fermions with two valence pion masses: 310 and 690~MeV. We use momentum-smeared sources to improve the signal up to nucleon boost momentum $P_z=2.18$~GeV, and determine nonperturbative renormalization factors in RI/MOM scheme. We compare our lattice results with the matrix elements obtained from matching the PDFs from CT18NNLO and NNPDF3.1NNLO global fits. Our data support the assumptions of strange-antistrange and charm-anticharm symmetry that are commonly used in global PDF fits, and we find smaller than expected parton distribution at mid to small $x$. [Preview Abstract] |
Friday, October 30, 2020 10:42AM - 10:54AM |
EM.00002: Gluon parton distribution function from Lattice QCD. Zhouyou Fan, Huey-Wen Lin, Rui Zhang The parton distribution functions (PDFs) are process-indenpendent information of the quark and gluon inside the hadron. Even though gluon PDF could be obtained from the global fit of the experimental data and dominates at the small x region, gluon PDF studies from theoretical side are much fewer then quark PDF. We present the results to access the x-dependence of the gluon unpolarized PDF inside nucleon using lattice QCD. The lattice calculation is carried out for the gluon PDF matrix element with the nucleon momentum up to 2.16 GeV, lattice spacing a$=$0.12 fm, pion mass 220 MeV, 310 MeV and 690 MeV. The matrix elements are extrapolated to the physical pion mass and then compared with the Fourier transform of the global fit CT18 of the gluon PDF. [Preview Abstract] |
Friday, October 30, 2020 10:54AM - 11:06AM |
EM.00003: Exploring Nucleon Spin Structure and Hadronization through Measuring Hadrons in Jets at STAR James Drachenberg The Solenoidal Tracker at RHIC (STAR) investigates nucleon spin structure through collisions of spin-polarized beams of protons. Asymmetries in the distributions of hadrons within jets produced in collisions of transversely polarized protons provide access to the transversity distribution function at a range of $x$ complementary to semi-inclusive deep inelastic scattering (SIDIS) experiments but at much higher $Q^2$. Asymmetries seen in STAR data collected in 2011 at $\sqrt{s}=500$ GeV and in 2012 at 200 GeV have given the first experimental hints that the universality of this ``Collins mechanism'' may extend to proton-proton collisions, as it does in SIDIS and $e^+e^-$. These data also provide unique insight to the transverse momentum dependence of the Collins asymmetry in jets, crucial for a deeper understanding of the Collins fragmentation function. The spin-averaged distributions of hadrons within jets may also provide a means to improve constraints on gluon fragmentation functions. The final 2011 and preliminary 2012 STAR hadron-in-jet asymmetries will be presented in context of global transversity analyses and model calculations. The status of the unpolarized hadron-in-jet analysis will be presented. [Preview Abstract] |
Friday, October 30, 2020 11:06AM - 11:18AM |
EM.00004: Simultaneous extraction of spin-dependent and spin-averaged gluon PDFs Yiyu Zhou, Nobuo Sato, Wally Melnitchouk, Jacob Ethier, Carlota Andres We made simultaneous extraction of spin averaged and spin dependent PDFs within multistep MC procedures, with combined analysis of inclusive unpolarized and polarized Jet from RHIC to Tevatron energies. By analyzing the preliminary results we had, we were able to further constrain on $\Delta g$. [Preview Abstract] |
Friday, October 30, 2020 11:18AM - 11:30AM |
EM.00005: Polarized Drell-Yan at SpinQuest/ Fermilab E1039 Noah Wuerfel The SpinQuest (Fermilab E1039) experiment will measure an azimuthal asymmetry in the Drell-Yan production of $\mu+$ $\mu-$ pairs from 120 GeV/c proton interactions with polarized nucleons to extract the Sivers function for $\bar{u}$ and $\bar{d}$. A nonzero asymmetry would be “smoking gun” evidence for orbital angular momentum of the light sea-quarks: a possible contributor to the proton’s spin. Measurements of a transverse single spin asymmetry in the J/$\Psi$ background would also serve to constrain the gluon Sivers function over $0.05 < x_{target} < 0.2$. The polarized target, developed by Los Alamos National Labs and University of Virginia, uses Dynamic Nuclear Polarization to reach an average proton target polarization over 80$\%$. After a brief introduction to the E1039 experimental apparatus and target, I will discuss upcoming physics at SpinQuest. [Preview Abstract] |
Friday, October 30, 2020 11:30AM - 11:42AM |
EM.00006: ABSTRACT Rescheduled to Session SL |
Friday, October 30, 2020 11:42AM - 11:54AM |
EM.00007: Systematic Study of Azimuthal Angle Reconstruction in SpinQuest Abinash Pun SpinQuest at Fermilab is a fixed-target Drell-Yan experiment intended to measure the light sea quark ($\bar{u}$ and $\bar{d}$) Sivers functions. An unpolarized 120 GeV proton beam from the Fermilab Main Injector and a transversely polarized NH$_3$ or ND$_3$ target will be used in the experiment. A non-zero value of the light sea quark Sivers functions will provide evidence of non-zero angular momentum of sea quarks, which can help us to better understand the spin structure in the nucleon. Since, the Sivers function arises from the transverse momentum of quarks inside a transversely polarized nucleon, our ability to correctly reconstruct the transverse properties of the dimuons produced from the Drell-Yan process is of primary importance. We need to reconstruct the direction (the azimuthal angle) of the transverse momentum from the observed muon tracks, and so we will study the resolution of that angle in reconstruction using simulation. We present the study of the migration matrix with simulation in the SpinQuest framework. The migration matrix is a quantitative way to describe the effect of the event reconstruction process on desired observables (azimuthal angle, transverse momentum, etc.), and can also be used to rebuild the truth distribution. [Preview Abstract] |
Friday, October 30, 2020 11:54AM - 12:06PM |
EM.00008: Systematic Study of Potential False Azimuthal Asymmetries in SpinQuest Md Forhad Hossain SpinQuest is a transversely polarized Drell-Yan experiment at Fermilab that will measure the Sivers asymmetry for the light antiquarks in the nucleon, using polarized $NH_3$ and $ND_3$ targets and the SeaQuest (E906) spectrometer. Measuring a non-zero Sivers asymmetry would provide strong evidence for non-zero sea-quark orbital angular momentum. There are many systematic effects that could generate false azimuthal asymmetries that could masquerade as a Sivers asymmetry; for example, the time-dependence of the spectrometer efficiency, the fluctuations of the beam luminosity, the position dependence of the interaction vertex, and the combinatorial background. In this presentation, we will discuss the studies of these systematic effects using both reconstructed data from the unpolarized Drell-Yan experiment SeaQuest and simulation. [Preview Abstract] |
Friday, October 30, 2020 12:06PM - 12:18PM |
EM.00009: Online monitoring software~at the E1039/SpinQuest experiment Catherine Ayuso The E1039/SpinQuest experiment is a transversely polarized fixed target experiment at Fermi National Accelerator Laboratory aiming to explore the sea quark and gluon Sivers functions via the measurement of single spin asymmetries for a number of physics processes including J/Psi, Psi' and Drell-Yan production. ~The experiment employs a 120-GeV extracted proton beam colliding with transversely-polarized NH3 and ND3 cryogenic targets and its spectrometer is optimized to detect the oppositely-charged muon pair output of these processes. In pursuit of these asymmetry measurements, we are seeking to develop an advanced GPU-based multi-threaded framework that allows an efficient parallelization of the online data processing, which will facilitate prompt online reconstruction, optimizations, and robust data quality monitoring.~This presentation will focus on the framework for this online monitoring software and report the current status of the experiment. [Preview Abstract] |
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