Direct- and Resolved-Photon Threshold Resummation for Polarized High-$p_T$ Hadron Production at COMPASS

TL;DR

This paper advances the understanding of polarized high-$p_T$ hadron production by analyzing both direct and resolved photon contributions, including threshold resummation, and compares results with COMPASS data.

Contribution

It provides a comprehensive next-to-leading logarithmic resummation of threshold corrections for both direct and resolved photon processes in polarized hadron production.

Findings

Resummation improves agreement with experimental data.

Resolved photon contributions are significant at high $p_T$.

Fragmentation functions critically influence spin asymmetry predictions.

Abstract

We complete our earlier study of the "direct" part of the cross section and spin asymmetry for the photoproduction process $\gamma N\rightarrow h X$ by analysing the "resolved" contribution, for which the photon couples like a hadron through its parton structure. The incident photon and nucleon are longitudinally polarized and one observes a hadron $h$ at high transverse momentum $p_T$. Soft or collinear gluon emissions generate large logarithmic threshold corrections which we resum to next-to-leading logarithmic order. We compare our results with recent spin asymmetry data by the COMPASS collaboration, highlighting the role of the fragmentation functions.