Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session LF: Proton Puzzles III |
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Chair: Jianwei Qiu, Jefferson Lab Room: Hilton King's 2 |
Saturday, October 27, 2018 9:00AM - 9:15AM |
LF.00001: The Pion Cloud and the Puzzle of the Proton 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. A natural explanation is that the sea arises from the pion cloud of the proton, which leads to an excess of dbar over ubar quarks. However, a theoretical explanation of the momentum dependence of the ratio of dbar to ubar measured by E866 remains a challenge. 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, 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. |
Saturday, October 27, 2018 9:15AM - 9:30AM |
LF.00002: Studies on Light Quark Flavor Asymmetry in the Nucleon Sea at SeaQuest Experiment Arun Tadepalli The Fermilab E906/SeaQuest is an experiment aimed at studying the anti-quark distributions in nucleons and nuclei. The experiment uses a 120 GeV proton beam extracted from the Main Injector at Fermilab. SeaQuest takes advantage of the Drell-Yan process to probe the anti-quark structure in the proton. In the Drell-Yan process, quark from one hadron annihilates with an anti-quark from another hadron, producing a virtual photon which eventually decays into dileptons. The SeaQuest forward spectrometer is designed to detect such dimuons generated by the Drell-Yan process. Ratio of cross-sections of the interaction of proton beam on liquid deuterium and hydrogen targets allows SeaQuest to map out $\overline{d}(x)/overline{ |
Saturday, October 27, 2018 9:30AM - 9:45AM |
LF.00003: Machine Learning and the Drell-Yan Cross-Section Ratios at E906 SeaQuest Daniel Morton Multivariate analysis has successfully been employed at high and medium energy experiments, especially for the detection of rare events, and is being utilized now by SeaQuest. The E906 SeaQuest spectrometer measures muons produced from the Fermilab 120 GeV proton Main Injector beam incident on liquid Hydrogen, Deuterium and solid C, Fe and W targets. Utilizing coincident muon pairs, SeaQuest is sensitive to the Drell-Yan process and thus acts as a probe into nucleon structure, in particular the flavor asymmetry in the nucleon sea. This is explored by developing cross-section ratios of the targets, but corrections are needed for yields of background processes. This talk will focus on how the cross-section ratio of the targets is derived, including identification and subtraction of backgrounds comparing machine learning and other methods. |
Saturday, October 27, 2018 9:45AM - 10:00AM |
LF.00004: Fermilab E1039 polarized target experimental apparatus and changes from SeaQuest/E906 L. Donald Isenhower Fermilab E1039 will be the first experiment to do polarized Drell-Yan measurements with sea antiquarks and is expected to start commissioning in the Fall of 2018. E1039 is expected to have 10,000 times higher statistics than the COMPASS II polarized measurements using pion valence quarks. E1039's polarized target will use ammonia, NH3 and ND3, to provide the hydrogen and deuterium targets. The ammonia will be polarized utilizing a superconducting magnet and a cooling system to keep the targets at 1 K. The target system will be described including its demonstrated ability to handle high beam rates with reasonable time cycles for re-polarization and replacing the custom targets. Changes being made to the shielding, beam line and monitoring, spectrometer, basic Data Acquisition systems, and other required components will be described and current status will be reported. Discussions of the software upgrades and the physics being studied will be covered by other talks at this conference. |
Saturday, October 27, 2018 10:00AM - 10:15AM |
LF.00005: Simulation and Reconstruction Effort for the E1039 Polarized Drell-Yan Experiment Haiwang Yu Among all efforts to solve the proton "spin puzzle", the Sivers function measurement is an important and unique one. Fully understanding the nucleon spin structure requires information on the orbital angular momentum (OAM) of quarks and gluons. Although the search for a rigorous, model-independent connection between the Sivers distribution and quark OAM is still ongoing, it is clear that a non-zero quark Sivers function requires non-zero quark OAM. The upcoming E1039 experiment at FermiLab is an upgrade of the previous E906 (SeaQuest) experiment, now with polarized proton and deuteron targets. The main goal is to measure the flavor dependent sea quark Sivers function through the Drell-Yan process with its unique sensitive kinematic region. To achieve this physics goal, many hardware and software efforts are underway. We will report the current status of the E1039 experiment, focusing on improvements to the simulation and reconstruction software. |
Saturday, October 27, 2018 10:15AM - 10:30AM |
LF.00006: The Measurement of the Seaquark Sivers Asymmetry in Fermilab E1039 Polarized Drell-Yan Experiment Mikhail Yurov Despite significant progress achieved in the past experimental measurements, the problem of the full description of the nucleon spin composition remains unresolved. As a continuing effort of this broad program, Fermilab E1039 experiment was proposed to access the sea quark Sivers function by measuring transverse single spin asymmetry in Drell-Yan production. These measurements will test if the sea quark orbital angular momentum contributes to the total nucleon spin. The upcoming E1039 experiment will utilize the 120 GeV unpolarized proton beam along with a transversely polarized ammonia target and the existing E906 SeaQuest detector package. We will report on the current status of the E1039 Drell-Yan experiment. |
Saturday, October 27, 2018 10:30AM - 10:45AM |
LF.00007: Fermilab E1039 Beyond Sea Quark Sivers Michael Daugherity The E906/SeaQuest experiment at Fermilab is studying the distributions of anti-quarks in the nucleon sea with 120 GeV protons interacting on solid and liquid targets. E1039 will extend these measurements using the existing spectrometer with an upgraded polarized proton and deuteron target. The primary goal of E1039 is to study transverse single spin asymmetry in Drell-Yan production to determine the Sivers function in sea quarks up to a Bjorken-x of 0.45. Additionally, E1039 allows for many other interesting opportunities including sea quark transversity measurements where existing data has large uncertainties, exploring possible sensitivity of $\frac{J}{\psi}$ production to the Sivers function, and a parasitic trigger for dimuons with a downstream vertex as predicted in various models of dark photon decay. This presentation will focus on these additional topics which can be explored by E1039. |
Saturday, October 27, 2018 10:45AM - 11:00AM |
LF.00008: Constraining the Sea Quark Distributions Through W+/- Cross Section Ratio Measurements at STAR Matthew R Posik
Over the past several years, parton distribution functions (PDFs) have become more precise. However there are still kinematic regions where more data are needed to help constrain global PDF extractions, such as the ratio of the sea quark distributions dbar/ubar near the valence region, x ≈ 0.1-0.3, where x is the fraction of the proton momentum carried by the parton. Furthermore, current measurements appear to suggest different high-x behaviors of this ratio. The W cross section ratio (W+/W-) is sensitive to the unpolarized u, d, ubar, and dbar quark distributions at large Q2 set by the W mass and could help shed light on this discrepancy. The STAR experiment at RHIC is well equipped to measure the leptonic decays of W bosons, in the mid-pseudorapidity range (|η|≤ 1), produced in proton + proton collisions at √s = 500/510 GeV. At these kinematics STAR is sensitive to quark distributions near x of 0.16. STAR can also measure W+/W- in a more forward region ranging from 1.0 < η < 1.5, which extends the sea quark sensitivity to higher x. RHIC runs from 2011 through 2013 have collected about 350 pb-1 of integrated luminosity, and a 2017 run will provide an additional 350 pb-1. This talk will present new preliminary results of the 2011-2013 W cross section ratios. |
Saturday, October 27, 2018 11:00AM - 11:15AM |
LF.00009: Abstract Withdrawn |
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