Collins asymmetries for pion-in-jet production in polarized $\ell p$ collisions at the EIC

TL;DR

This paper investigates Collins azimuthal asymmetries in pion-in-jet production during polarized lepton-proton collisions at the EIC, using a simplified TMD approach to enhance understanding of transversity distributions.

Contribution

It extends previous analyses to a simpler process, computes asymmetries at EIC, and discusses the potential for testing TMD universality and factorization.

Findings

Quark-initiated channels dominate the asymmetries.

Gluon contributions are marginal in the considered kinematics.

Comparison with future EIC data can test TMD universality.

Abstract

We study Collins azimuthal asymmetries for pion-in-jet production in polarized lepton-proton collisions, extending previous analyses of polarized $pp$ scattering to a complementary and theoretically simpler process. We keep adopting a simplified transverse momentum dependent (TMD) approach, with a collinear configuration for the initial state, and employ the transversity and Collins fragmentation functions as extracted from semi-inclusive deep inelastic scattering and $e^+ e^-$ annihilation processes. We then compute azimuthal asymmetries for the Electron-Ion Collider (EIC) kinematics, both within a leading order (LO) approach and by including quasireal photon exchange in the Weizs\"acker-Williams approximation. Although this contribution is relevant in the whole kinematical range explored, it does not spoil the dominance of quark-initiated channels, leaving only a marginal role to their gluon counterparts. In this respect, Collins asymmetries in lepton-proton processes allow for a much clearer access to the transversity distribution, including its sea-quark component. As we will argue, a comparison with future EIC data could represent a further step in testing the hypothesis of the universality of the Collins function as well as of the TMD factorization for this class of processes.