Kinematics of Current Region Fragmentation in Semi-Inclusive Deeply Inelastic Scattering

TL;DR

This paper investigates the kinematic boundaries of the current fragmentation region in semi-inclusive deep inelastic scattering, emphasizing the importance of unified descriptions across rapidity regions at moderate energy scales.

Contribution

It introduces criteria to identify the current fragmentation region and discusses the overlap of rapidity regions, proposing a more comprehensive approach for SIDIS analysis.

Findings

Significant overlap exists between rapidity regions at a few GeV scales.

Current criteria may need refinement for accurate region identification.

Unified descriptions should encompass all rapidities for better SIDIS modeling.

Abstract

Different kinematical regimes of semi-inclusive deeply inelastic scattering (SIDIS) processes correspond to different underlying partonic pictures, and it is important to understand the transition between them. This is particularly the case when there is sensitivity to intrinsic transverse momentum, in which case kinematical details can become especially important. We address the question of how to identify the current fragmentation region --- the kinematical regime where a factorization picture with fragmentation functions is appropriate. We distinguish this from soft and target fragmentation regimes. Our criteria are based on the kinematic regions used in derivations of factorization theorems. We argue that, when hard scales are of order a few GeVs, there is likely significant overlap between different rapidity regions that are normally understood to be distinct. We thus comment on the need to take this into account with more unified descriptions of SIDIS, which should span all rapidities for the produced hadron. Finally, we propose general criteria for estimating the proximity to the current region at large Q.