Gauge invariance and kaon production in deep inelastic scattering at low scales

TL;DR

This paper investigates how hadron mass effects influence semi-inclusive kaon production in deep inelastic scattering, demonstrating that accounting for these corrections reconciles experimental discrepancies between different collaborations.

Contribution

It introduces a gauge-invariant, mass-dependent factorization framework for kaon production in DIS at low scales, improving agreement with experimental data.

Findings

Hadron mass corrections significantly reduce discrepancies in kaon multiplicity measurements.

Mass-dependent scaling variables reconcile $K^+ + K^-$ multiplicities between experiments.

The framework respects gauge invariance at leading order and twist.

Abstract

This paper focuses on hadron mass effects in calculations of semi-inclusive kaon production in lepton-Deuteron deeply inelastic scattering at HERMES and COMPASS kinematics. In the collinear factorization framework, the corresponding cross section is shown to factorize, at leading order and leading twist, into products of parton distributions and fragmentation functions evaluated in terms of kaon- and nucleon-mass-dependent scaling variables, and to respect gauge invariance. It is found that hadron mass corrections for integrated kaon multiplicities sizeably reduce the apparent large discrepancy between measurements of $K^+ + K^-$ multiplicities performed by the two collaborations, and fully reconcile their $K^+/K^-$ ratios.