Theoretical estimate on tensor-polarization asymmetry in proton-deuteron Drell-Yan process

S. Kumano and Qin-Tao Song
Phys. Rev. D 94, 054022 – Published 20 September 2016

Abstract

Tensor-polarized parton distribution functions are new quantities in spin-1 hadrons such as the deuteron, and they could probe new quark-gluon dynamics in hadron and nuclear physics. In charged-lepton deep inelastic scattering, they are studied by the twist-2 structure functions b1 and b2. The HERMES Collaboration found unexpectedly large b1 values compared to a naive theoretical expectation based on the standard deuteron model. The situation should be significantly improved in the near future by an approved experiment to measure b1 at Thomas Jefferson National Accelerator Facility (JLab). There is also an interesting indication in the HERMES result that finite antiquark tensor polarization exists. It could play an important role in solving a mechanism on tensor structure in the quark-gluon level. The tensor-polarized antiquark distributions are not easily determined from the charged-lepton deep inelastic scattering; however, they can be measured in a proton-deuteron Drell-Yan process with a tensor-polarized deuteron target. In this article, we estimate the tensor-polarization asymmetry for a possible Fermilab Main-Injector experiment by using optimum tensor-polarized parton distribution functions to explain the HERMES measurement. We find that the asymmetry is typically a few percent. If it is measured, it could probe new hadron physics, and such studies could create an interesting field of high-energy spin physics. In addition, we find that a significant tensor-polarized gluon distribution should exist due to Q2 evolution, even if it were zero at a low Q2 scale. The tensor-polarized gluon distribution has never been observed, so it is an interesting future project.

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  • Received 9 June 2016

DOI:https://doi.org/10.1103/PhysRevD.94.054022

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Particles & Fields

Authors & Affiliations

S. Kumano1,2,3 and Qin-Tao Song1,3

  • 1KEK Theory Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), 1-1, Ooho, Tsukuba, Ibaraki 305-0801, Japan
  • 2J-PARC Branch, KEK Theory Center, Institute of Particle and Nuclear Studies, KEK, and Theory Group, Particle and Nuclear Physics Division, J-PARC Center, 203-1, Shirakata, Tokai, Ibaraki 319-1106, Japan
  • 3Department of Particle and Nuclear Physics, Graduate University for Advanced Studies (SOKENDAI), 1-1, Ooho, Tsukuba, Ibaraki 305-0801, Japan

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Issue

Vol. 94, Iss. 5 — 1 September 2016

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