Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons

TL;DR

This paper proposes a method to directly measure linearly polarized gluons inside unpolarized hadrons through specific asymmetries in electron-hadron collisions, with implications for future collider experiments.

Contribution

It introduces a direct probing technique for linearly polarized gluons via cos(2 phi) asymmetries in jet and heavy quark pair production, and discusses their experimental feasibility.

Findings

Maximal cos(2 phi) asymmetries estimated for future experiments.

Feasibility of measuring linearly polarized gluon distributions at EIC and LHeC.

Analysis of factorization breaking effects in hadron-hadron collisions.

Abstract

We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos (2 phi) asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future EIC or LHeC experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow to quantify the importance of initial and final state interactions.