New ways to access the transverse spin content of the nucleon

TL;DR

This paper proposes novel experimental methods to access the transversity distributions of the nucleon, involving interference effects in photoproduction and exclusive meson pair production, with promising rate estimates.

Contribution

It introduces new approaches to measure chiral-odd transversity GPDs and parton distributions through interference effects in specific photoproduction processes.

Findings

Interference with Bethe-Heitler or Drell-Yan amplitudes enables access to transversity distributions.

Perturbative calculations show feasible rates in high and medium energy regimes.

Methods are applicable to electron-ion collider experiments.

Abstract

We first describe a new way to access the chiral odd transversity parton distribution in the proton through the photoproduction of lepton pairs. The basic ingredient is the interference of the usual Bethe-Heitler or Drell-Yan amplitudes with the amplitude of a process, where the photon couples to quarks through its chiral-odd distribution amplitude, which is normalized to the magnetic susceptibility of the QCD vacuum. We also show how the chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive electro - or photoproduction process of a meson pair with a large invariant mass and when the final nucleon has a small transverse momentum. We calculate perturbatively the scattering amplitude at leading order, both in the high energy domain which may be accessed in electron-ion colliders and in the medium energy range. Estimated rates are encouraging.