Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S15: Nucleon Structure and Spin ILive
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Sponsoring Units: GHP Chair: Yong Zhao, Brookhaven National Laboratory |
Monday, April 19, 2021 1:30PM - 1:42PM Live |
S15.00001: N3LO extraction of the Sivers function from SIDIS, Drell-Yan and W$+$-/Z data. Alexei Prokudin, Alexey Vladimirov, Marcin Bury We perform the global analysis of polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), pion-induced polarized Drell-Yan (DY), and W$+$-/Z boson production data and extract the Sivers function for u, d, s, and and for sea-quarks. We use the framework of transverse momentum dependent factorization at NLO accuracy. The Qiu-Sterman function is determined in a model-independent way from the extracted Sivers function. We also evaluate the significance of the predicted sign change of Sivers function in DY with respect to SIDIS. [Preview Abstract] |
Monday, April 19, 2021 1:42PM - 1:54PM Live |
S15.00002: Diffractive DVCS and two meson production at an electron-ion collider Wim Cosyn, Bernard Pire, Lech Szymanowski In high energy electron-ion colliders, a new way to probe nucleon structure becomes available through diffractive reactions, where the incident particle produces a very energetic almost forward particle. QCD describes these reactions as due to the exchange of a Pomeron which may be perturbatively described as a dressed two-gluon state, provided a hard scale allows the factorization of the amplitude. In this talk, we consider two diffractive exclusive processes that give access to hadronic structure in terms of the generalized parton distributions (GPDs): 1) electroproduction of a forward $\rho$ meson and a timelike deeply virtual photon, 2) electro- and photoproduction of two mesons. In both reactions we consider kinematics where the two produced particles are separated by a large rapidity gap. The GPDs enter in these reactions in a specific way: only quarks enter, and only the so-called ERBL region contributes. We show estimates for these processes at the future electron-ion collider for proton and deuteron beams, and discuss the dependence on non-perturbative inputs (GPDs, distribution amplitudes). [Preview Abstract] |
Monday, April 19, 2021 1:54PM - 2:06PM Live |
S15.00003: Updates on the neutron $F_2$ extraction with CJ15 PDFs Shujie Li The CJ (CTEQ-Jefferson Lab) Collaboration provides a global fit of parton distribution functions (PDFs) with a special emphasis on the large x region with deuteron nuclear corrections at the parton level. By applying the same nuclear corrections on the world DIS $F_2$ datasets, we performed a data-driven extraction of neutron $F_2$. That dataset has been used for applications such as neutron excess corrections on experimental data and moments calculations. In this work we present an updated $F_2^n$ datasets with detailed uncertainty analysis. Within the same framework, we also provide the neutral-current and charged-current structure functions of proton, deuteron, and neutron that are calculated from PDFs. [Preview Abstract] |
Monday, April 19, 2021 2:06PM - 2:18PM Not Participating |
S15.00004: Residual Mean Field Model of Valence Quarks in the Nucleon Misak Sargsian, Christopher Leon We develop a non-perturbative model for valence PDFs based on the quark interactions in the mean field of the nucleonic interior. The model is based on the separation of valence 3q system from the residual system which is the source of the mean field. The PDFs are calculated within effective light-front diagrammatic approach which allows to introduce light-front valence quark and residual wave functions. The model allows us to obtain a new relation between the position of the peak of xq$_{\mathrm{V}}$(x) distribution of the valence quark and the effective mass of the residual system,m$_{\mathrm{R}}$: x$_{\mathrm{p}}$ \textasciitilde 1/4(1-m$_{\mathrm{R}}$/m$_{\mathrm{N}})$ and explains the difference in the peak positions for d- and u- quarks due to expected larger residual mass in the case of valence d- quarks We evaluated the Q$^{\mathrm{2}}$ dependence of the mass of the residual system and its effective size which gives a new insight on the effects of the QCD evolution on mean field of the nucleon. The evaluated wave functions of valence 3q- and residual systems can be used in calculations of other observables such as nucleon form factors, generalized and transverse momentum distributions. [Preview Abstract] |
Monday, April 19, 2021 2:18PM - 2:30PM Live |
S15.00005: Studying Nucleon Structure in $A=3$ Nuclei using Double Spectator Tagging at the EIC Jackson Pybus, Ivica Friščić, Dien Nguyen Due to the lack of free neutron targets, the structure functions of the neutron are determined using deuterium or $^3$He targets. In such experiments, nuclear effects can lead to very large model dependencies in interpreting data. Experiments on the deuteron, such as BONUS in Hall B of Jefferson Lab, seek to minimize the model dependencies by tagging low-momentum recoiling protons to ensure that the struck neutron was nearly on-shell. To date, such a technique has not been possible with $^3$He, which is the preferred target for examining neutron spin structure via polarized scattering. We will show that, with the advent of the Electron-Ion Collider and its unique far-forward detection capabilities, it will be possible to tag on recoil protons with low momentum in the ion rest frame. This will allow a determination of neutron spin structure with far less model-dependence, as well as to further our understanding of the EMC effect by tagging high-momentum recoil protons. [Preview Abstract] |
Monday, April 19, 2021 2:30PM - 2:42PM Live |
S15.00006: Polarized electron-deuteron DIS with spectator nucleon tagging Christian Weiss, Wim Cosyn Polarized electron-deuteron DIS with detection of a spectator proton (spectator tagging) represents a unique method for extracting the neutron spin structure functions and studying spin-dependent nuclear modifications. The measured proton momentum fixes the nuclear configuration during the DIS process and enables a differential treatment of nuclear effects. We present a theoretical framework for polarized deuteron DIS with spectator tagging [1]. The spin density matrix formalism is used to describe general deuteron polarization (vector, tensor). Light-front quantum mechanics is employed to separate nuclear and nucleonic structure in the high-energy process. The spin-dependent light-front momentum distribution of the neutron in the polarized deuteron are computed and studied as functions of the tagged proton momentum. It is shown that the tagged proton momentum can be used to control the effective neutron polarization in the DIS process and eliminate D-wave depolarization. The free neutron structure functions can be obtained by pole extrapolation. Such measurements could be performed at the EIC with polarized deuteron beams and forward proton detectors. [1] W. Cosyn, C. Weiss, Phys. Rev. C 102, 065204 (2020) [Preview Abstract] |
Monday, April 19, 2021 2:42PM - 2:54PM Not Participating |
S15.00007: Probing Nucleon Structure in Drell-Yan and J/$\psi $ production at COMPASS April Townsend COMPASS is a fixed target experiment in the North Area of CERN. One of the primary goals of its broad physics program is to study the Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs) that describe the spin structure of nucleons. COMPASS accesses the TMD PDFs via the measurement of azimuthal asymmetries in the Drell-Yan (DY) process and in hadron production in Semi-Inclusive Deep Inelastic Scattering (SIDIS). Measurements of Sivers asymmetries are particularly important as they can be used to test the predicted process dependence of the Sivers TMD PDFs, which are expected to have opposite sign when measured in SIDIS and DY. In 2015 and 2018, COMPASS collected DY data by scattering a negative pion beam off a transversely polarized ammonia target. Preliminary COMPASS results are consistent with the predicted sign change of the Sivers function. During the DY data taking, COMPASS also collected a large sample of J/$\psi $ events. Single-spin asymmetries in J/$\psi $ production may give access to the gluon Sivers PDF and improve our understanding of the J/$\psi $ production mechanisms. The reconstruction of COMPASS experimental and Monte-Carlo data was realized exploiting the parallel computing resources of the Blue Waters (NCSA) and the Frontera (TACC) supercomputers. [Preview Abstract] |
Monday, April 19, 2021 2:54PM - 3:06PM Live |
S15.00008: First Analysis of the World Polarized DIS Data in the Small-$x$ Dipole Formalism Yuri Kovchegov, Daniel Adamiak, Wally Melnitchouk, Daniel Pitonyak, Nobuo Sato, Matthew Sievert We present a Monte-Carlo-based analysis in the Jefferson Angular Momentum (JAM) collaboration framework of the combined world polarized deep inelastic scattering (DIS) data at moderately small values of the Bjorken $x$ variable ($0.01 |
Monday, April 19, 2021 3:06PM - 3:18PM Live |
S15.00009: Renormalizing the Quasi-PDF Operator under Lattice Regularization Yushan Su, Yi-Kai Huo, Long-Cheng Gui, Xiangdong Ji, Yuan-Yuan Li, Maximilian Schlemmer, Peng Sun, Yi-Bo Yang, Kuan Zhang In large-momentum effective theory, renormalization of the Euclidean operators in lattice regularization is a challenge due to the linear divergences in the self-energy of Wilson lines. Based on the Lattice QCD matrix elements of the quasi-PDF operator at $a$= 0.03fm $\sim$ 0.12 fm with clover and overlap valence quarks on staggered and domain-wall sea, we design a strategy to disentangle the divergent renormalization factors from finite physics matrix elements which can be matched to a continuum scheme at short distance such as dimensional regularization and minimal subtraction. Our results indicate that the renormalization factors are universal in the chiral fermion formalism but not in the clover case. However, the physical matrix elements appear independent of the valence fermion formulations. Moreover, we find a large non-perturbative effect in the popular RI/MOM and ratio renormalization scheme used previously, which supports the hybrid renormalization procedure proposed recently. [Preview Abstract] |
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