On the role of Collins effect in the single spin asymmetry A_N in p(transv. polarized) p --> h X processes

TL;DR

This paper investigates the contribution of the Collins effect to the transverse single spin asymmetry A_N in polarized proton-proton collisions, revising previous estimates and discussing phenomenological implications using recent data.

Contribution

It provides corrected estimates of the Collins effect's role in A_N, incorporating recent Collins function extractions and clarifying its significance in the observed asymmetry.

Findings

The Collins effect contribution is less suppressed than previously thought.

Updated estimates using recent Collins functions suggest a more significant role.

Phenomenological analysis aligns with experimental observations.

Abstract

The much debated issue of the transverse single spin asymmetry A_N observed in the inclusive large P_T production of a single hadron in pp interactions, p(transv. polarized) p --> pion X, is considered in a TMD factorization scheme. A previous result [1,2] stating that the maximum contribution of the Collins effect is strongly suppressed, is revisited, correcting a numerical error. New estimates are given, adopting the Collins functions recently extracted from SIDIS and e+e- data, and phenomenological consequences are discussed.