Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session C09: 3D Quark and Gluon Structure of the Proton |
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Sponsoring Units: GHP DNP Chair: David Richards, Jefferson Lab Room: Sheraton Governor's Square 11 |
Saturday, April 13, 2019 1:30PM - 1:42PM |
C09.00001: The future EIC program and its impact on hadron tomography and HEP phenomenology Timothy J Hobbs As embodied by its placement in the 2015 Nuclear Science Long Range Plan and subsequent NAS Report, the goal of designing and constructing a high-luminosity electron-ion collider (EIC) is crucial to the future of hadron/particle physics. This machine will dramatically enhance our knowledge of a wide array of phenomena at work in QCD bound states, including a comprehensive mapping of the partonic substructure of hadrons --- especially for the proton and lighter mesons. While these explorations of hadron structure will necessarily extend to transverse momentum-dependent observables, in this talk I will concentrate on the prospects for an EIC to sharpen our understanding of the proton's collinear parton distribution functions (PDFs) and derived quantities covering a wide energy spectrum, including Mellin moments calculable on the QCD lattice and theoretical predictions for Higgs production at hadron colliders. On this basis, I will outline the impact we can expect from an EIC on our understanding of hadrons' internal tomography at lower energies as well as the role it will play enhancing the discovery potential along the energy frontier. |
Saturday, April 13, 2019 1:42PM - 1:54PM |
C09.00002: E1039/SpinQuest Polarized Drell-Yan Experiment at Fermilab Chun-Min Jen E1039, now named SpinQuest, is not only the successor to a series of unpolarized, fixed-target SeaQuest experiments but also the first transversally-polarized Drell-Yan experiment at Fermilab. SpinQuest data-taking begins this coming Fall 2019. In SpinQuest, a transversely-polarized NH3 or ND3 target is employed with the unpolarized, 120-GeV proton beam split from Fermilab main injector, to obtain measurements of the transverse single spin asymmetry, aka the Sivers asymmetry, without the need to account for fragmentation effects. If we observe a non-zero Sivers asymmetry, then the sea quarks' orbital angular momentum (OAM) contribution to the spin inside the nucleon must also be non-zero. A perceptible, non-vanishing OAM from the sea quarks would help to uncover the origin of the proton spin. Since the beginning of the SpinQuest commissioning in Fall 2018, we've implemented a wide range of changes on various systems such as the target, beam-line monitoring instrumentation, spectrometer, trigger, data acquisition, online event display, slow control, offline tracking reconstruction, simulation and software framework. In this talk, we will report on the current status of SpinQuest. |
Saturday, April 13, 2019 1:54PM - 2:06PM |
C09.00003: The systematic uncertainty and measurement approach of the sea quark Sivers Function of the Fermilab SpinQuest experiment. Arthur Conover More than three decades after the initial spin crisis there is still much uncertainty concerning the internal dynamics of the partons inside the nucleon. As an essential step in solving the crisis, Fermilab’s SpinQuest experiment (E1039) will for the first time measure the sign, magnitude and shape of the sea quark Sivers function with sub-percent precision. The experiment will take advantage of Fermilabs’s 120 GeV proton beam at the greatest instantaneous proton intensity ever on a dynamically vertically polarized solid target. The prospects of the measurement and the projected uncertainties of the SpinQuest experiment will be discussed. |
Saturday, April 13, 2019 2:06PM - 2:18PM |
C09.00004: Luminosity Measurement at an Electron Ion Collider Charles Earl Hyde The physics program of a future Electron Ion Collider (EIC) requires high precision measurement of the instantaneous and integrated luminosity. For polarized light ions, the luminosity must be measured independently for each polarization combination of the two beams. Also, the polarization dependence of the luminosity measure must be understood. The luminosity measurement techniques must be applicable with stable precision across the entire periodic chart of possible ion beam species. Relative luminosity, tagged to the individual stored bunches, is also required. I will review some possible techniques to measure the luminosity, and discuss the associated detector requirements. Possible techniques include: Van der Meer scans (V. Balagura, NIM A 654 (2011) 634); QED Compton (E. Aaron,H1 collaboration, Eur. Phys. J. C 72 (2012) 2163); Bremsstrahlung total absorption Calorimetry and Pair-Spectrometer (L. Adamczyk et al.,Nucl.Instrum.Meth. A744 (2014) 80). |
(Author Not Attending)
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C09.00005: The pressure distribution and shear forces inside the proton from lattice QCD Phiala Shanahan The distributions of pressure and shear forces inside the proton have recently been investigated for the first time using lattice Quantum Chromodynamics (LQCD) calculations of the energy momentum tensor. I will describe the results and discuss the utility of LQCD calculations in exploring, and supplementing, the assumptions in a recent extraction of the pressure distribution in the proton from deeply virtual Compton scattering. More generally, I will discuss the status and prospects of LQCD studies of the gluon structure of hadrons and light nuclei, motivated by providing Standard Model predictions for quantities to be measured for the first time at a planned Electron-Ion Collider. |
Saturday, April 13, 2019 2:30PM - 2:42PM |
C09.00006: Top quark pair production as a window into polarized quark and gluon distributions in pp scattering Gary R Goldstein Top-antitop pairs are produced prolifically in p+p collisions at the LHC, primarily by gluon fusion. At intermediate values of momentum fraction x for each gluon in g+g to t+tbar, the spin dependences of gluon distributions leave imprints on the momentum and spin correlations of the top pairs. These correlations are distinguishable from the quark-antiquark annihilation mechanism. Decays of such spin entangled top pairs through dilepton, single lepton and pure jet channels produce a variety of correlations among pairs of the 3-momenta of the decay products - particles and jets. These different angular correlations will be presented and related to measurable distributions of pairs of jets and/or leptons. Some models for spin dependent gluon transverse momentum distributions and generalized transverse momentum distributions will be used to simulate top pair decay product spin correlations, illustrating how to measure the gluon or quark polarizations in the colliding protons. |
Saturday, April 13, 2019 2:42PM - 2:54PM |
C09.00007: Extraction of Observables from Deeply Virtual Electron Proton Scattering Experiments Brandon Kriesten, Simonetta Liuti Imaging the 3D partonic structure of the nucleon is a fundamental goal of every major nuclear experimental program, including the EIC. Ji first proposed Deeply Virtual Compton Scattering (DVCS) as a probe for understanding the spatial distribution of the partons by fourier transform of the exchanged momentum transfer between the initial and final proton. The extraction of observables from Deeply Virtual Exclusive Reactions in a clear and concise formalism, such that the various twist components and angular dependencies can be untangled, is key. We present a completely covariant description of the DVCS process. In our helicity formalism, we can separate kinematic subleading terms from dynamic twist, given by the Q2 suppression and azimuthal angle ɸ. Since the higher twist terms are characterized by their dependence on ɸ, it is important to understand the angular contribution arising from the kinematics and separate it from the characteristic angular dependence of the higher twist terms. The extension to other Deeply Virtual Exclusive Reactions, such as TCS, is in progress. From our formalism, one can extract observables important in understanding the physical properties of the proton such as the angular momentum of the quarks and gluons inside the proton. |
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