Structure functions in the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons: II. parton model

TL;DR

This paper investigates the structure functions in polarized Drell-Yan processes involving spin-1/2 and spin-1 hadrons within a parton model framework, revealing new tensor polarized distributions and their experimental implications.

Contribution

It introduces tensor polarized distributions for spin-1 hadrons and identifies the number of relevant structure functions, highlighting differences from proton-proton reactions.

Findings

19 predicted structure functions reduce to 4 or 5 in practical cases

Tensor polarized distribution b_1 is identified and measurable

Antiquark tensor polarization can be extracted more easily in Drell-Yan processes

Abstract

We analyze the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons in a parton model. Quark and antiquark correlation functions are expressed in terms of possible combinations of Lorentz vectors and pseudovectors with the constrains of Hermiticity, parity conservation, and time-reversal invariance. Then, we find tensor polarized distributions for a spin-1 hadron. The naive parton model predicts that there exist 19 structure functions. However, there are only four or five non-vanishing structure functions, depending on whether the cross section is integrated over the virtual-photon transverse momentum \vec Q_T or the limit Q_T->0 is taken. One of the finite structure functions is related to the tensor polarized distribution b_1, and it does not exist in the proton-proton reactions. The vanishing structure functions should be associated with higher-twist physics. The tensor distributions can be measured by the quadrupole polarization measurements. The Drell-Yan process has an advantage over the lepton reaction in the sense that the antiquark tensor polarization could be extracted rather easily.