Improvement for Color Glass Condensate factorization: single hadron production in pA collisions at next-to-leading order

TL;DR

This paper introduces a systematic method to regularize rapidity divergences in CGC factorization, enabling more precise NLO calculations for single hadron production in pA collisions and addressing previous theoretical uncertainties and negativity issues.

Contribution

It proposes a new regularization approach for rapidity divergences in CGC, improving the accuracy and reliability of higher order calculations in high-energy pA collisions.

Findings

Automatic emergence of kinematic constraints with different values

Reduced theoretical uncertainty at NLO compared to LO

Overcoming negativity problem through proper scale choice

Abstract

High order calculation at semi-hard scale is very important, but a satisfactory calculation framework is still missing. We propose a systematic method to regularize rapidity divergences in the CGC factorization, which makes higher order calculation rigorous and straight forward. By applying this method to single hadron production in pA collision, we find the kinematic constraint effect introduced by hand in previous works comes out automatically, but with different values. The difference is crucial for our next-to-leading order (NLO) result to have a smaller theoretical uncertainty comparing with LO result, which makes high order calculation in CGC factorization to be useful. As a byproduct, the negativity problem found in literature can also be overcome in our framework by a proper choosing of factorization scale.