Dihadron helicity correlation in photon-nucleus collisions

TL;DR

This paper studies how the helicity correlation of back-to-back hadron pairs in photon-nucleus collisions can reveal details about spin transfer and fragmentation functions, with predictions for future collider experiments.

Contribution

It introduces a detailed analysis of dihadron helicity correlations in photon-nucleus collisions, including helicity amplitudes and numerical predictions for upcoming experiments.

Findings

Predictions for dihadron helicity correlations at EIC and RHIC/LHC.

Insights into flavor dependence of spin-dependent fragmentation functions.

Potential to probe circularly polarized gluon fragmentation functions.

Abstract

The helicity correlation of two back-to-back hadrons is a powerful tool that makes it possible to probe the longitudinal spin transfer, $G_{1L}$, in unpolarized hadronic collisions. In this work, we investigate the helicity correlation of back-to-back dihadrons produced in photon-nucleus collisions with both space-like and quasireal photons and explore its potential in understanding the flavor dependence of spin-dependent fragmentation functions. We present helicity amplitudes of partonic scatterings with both virtual and real photons and make numerical predictions for the dihadron helicity correlations at the future Electron Ion Collider experiment and the current RHIC/LHC ultra-peripheral collision experiment. Future experimental measurements can also illuminate the fragmentation function of circularly polarized gluons.