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

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.

Forward hadron productions in proton-proton collisions in small-xformalism

“…As discussed in Ref. [39,40,44], the light cone energy conservation provides the kinematical constraint on ξ as follows…”

“…These studies included a subset of next-to-leading order (NLO) corrections. The pursuit of complete NLO calculations began several years ago [26,[36][37][38][39][40][41]. In Refs.…”

Single inclusive hadron production in pA collisions at NLO

“…There have been several proposals to solve this problem, e.g. [10,11,12]. Here we propose an alternative way by introducing an explicit rapidity factorization scale when subtracting the rapidity divergence, similarly to what is done to absorb the collinear divergence in the DGLAP evolution of the parton distribution functions and fragmentations functions.…”

Heavy quarks in proton-nucleus collisions: The hybrid formalism

“…More recent discussions focus on the eventual relevance of additional collinear resummations at small x [29,30] and on the correct choice of the factorisation scale for the high-energy evolution [31,32]. In the previous publication [33], we have introduced a restriction on the lifetime of the partonic fluctuations of the projectile and also revisited the choice of scales. These considerations led to modified NLO expressions which later were shown to improve considerably the stability of the results and their agreement with experimental data [34].…”

“…As discussed above, single inclusive hadron production in the hybrid formalism has been the focus of a large number of recent publications [23,24,[26][27][28][31][32][33][34] . The result of this series of papers is a CGC-based computation performed at a full NLO accuracy in massless QCD.…”