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 and . The HERMES Collaboration found unexpectedly large 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 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 evolution, even if it were zero at a low scale. The tensor-polarized gluon distribution has never been observed, so it is an interesting future project.
2 More- Received 9 June 2016
DOI:https://doi.org/10.1103/PhysRevD.94.054022
© 2016 American Physical Society