Single-inclusive particle production in proton-nucleus collisions at next-to-leading order in the hybrid formalism

TL;DR

This paper refines the next-to-leading order calculation of single inclusive hadron production in proton-nucleus collisions within the hybrid formalism, emphasizing precise rapidity interval specification, wave function fluctuation considerations, and avoiding large number of colors approximation.

Contribution

It provides a more precise and unambiguous NLO calculation in the hybrid formalism, differing from previous results by clarifying evolution intervals and fluctuation effects.

Findings

Clarified the rapidity interval for evolution.

Introduced an Ioffe time cutoff for projectile fluctuations.

Derived NLO expressions without large number of colors approximation.

Abstract

We reconsider the perturbative next-to-leading calculation of the single inclusive hadron production in the framework of the hybrid formalism, applied to hadron production in proton-nucleus collisions. Our analysis, performed in the wave function approach, differs from the previous works in three points. First, we are careful to specify unambiguously the rapidity interval that has to be included in the evolution of the leading-order eikonal scattering amplitude. This is important, since varying this interval by a number of order unity changes the next-to-leading order correction that the calculation is meant to determine. Second, we introduce the explicit requirement that fast fluctuations in the projectile wave function which only exist for a short time are not resolved by the target. This Ioffe time cutoff also strongly affects the next-to-leading order terms. Third, our result does not employ the approximation of a large number of colors. Our final expressions are unambiguous and do not coincide at next-to-leading order with the results available in the literature.