Transversity studies with protons and light nuclei

TL;DR

This paper reviews a formalism for calculating time-reversal odd transverse momentum dependent parton distributions, applying it to proton models and nuclear effects, with results consistent with theoretical sum rules.

Contribution

It introduces a formalism for T-odd TMDs and applies it to different proton models and nuclear effects, providing insights into their behavior and sum rule fulfillment.

Findings

Results fulfill the Burkardt sum rule.

Nuclear effects are under theoretical control.

Models agree with sum rule expectations.

Abstract

A general formalism to evaluate time-reversal odd transverse momentum dependent parton distributions (T-odd TMDS) is reviewed and applied to the calculation of the leading-twist quantities, i.e., the Sivers and the Boer-Mulders functions. Two different models of the proton structure, namely a non relativistic constituent quark model and the MIT bag model, have been used. The results obtained in both frameworks fulfill the Burkardt sum rule to a large extent. The calculation of nuclear effects in the extraction of neutron single spin asymmetries in semi-inclusive deep inelastic scattering off transversely polarized $^3$He is also illustrated. It is found that the nuclear effects described by an Impulse Approximation approach are under theoretical control.