The nucleon's transversity and the photon's distribution amplitude probed in lepton pair photoproduction

TL;DR

This paper proposes a novel experimental method to measure the transversity distribution in protons and the photon distribution amplitude by analyzing lepton pair photoproduction with polarized targets, leveraging interference effects.

Contribution

It introduces a new approach to access the chiral-odd transversity distribution and photon distribution amplitude via interference in lepton pair photoproduction.

Findings

Enables experimental scanning of transversity distribution shape

Provides a method to probe photon distribution amplitude

Utilizes interference between Bethe Heitler, Drell-Yan, and photon coupling amplitudes

Abstract

We describe a new way to access the chiral odd transversity parton distribution in the proton through the photoproduction of lepton pairs on transversely polarized target. The basic ingredient is the interference of the Bethe Heitler or Drell-Yan amplitudes with the amplitude of a process, where the photon couples to quarks through its twist-2 chiral-odd distribution amplitude. This approach permits to scan experimentally the shape of the transversity distribution in a nucleon as well as the photon distribution amplitude.