Kaon Distribution Functions from Empirical Information

TL;DR

This paper develops a data-driven method to determine detailed parton distribution functions for pions and kaons using Drell-Yan data, avoiding reliance on hadron structure theories.

Contribution

It introduces a novel approach combining structure-function constraints and an all-orders exact evolution scheme to extract meson parton distributions directly from experimental data.

Findings

Obtained qualitatively sound light-meson structure features.

Identified the need for more precise data on u-quark distributions.

Highlighted the importance of direct u^K extraction for accuracy.

Abstract

Using available information from Drell-Yan data on pion and kaon structure functions, an approach is described which enables the development of pointwise profiles for all pion and kaon parton distribution functions (DFs) without reference to theories of hadron structure. The key steps are construction of structure-function-constrained probability-weighted ensembles of valence DF replicas and use of an evolution scheme for parton DFs that is all-orders exact. The DFs obtained express qualitatively sound features of light-meson structure, e.g., the effects of Higgs boson couplings into QCD and the size of heavy-quark momentum fractions in light hadrons. In order to improve the results, additional and more precise data on the $u$-quark-in-kaon, $u^K$, to $u$-quark-in-pion, $u^\pi$, DF ratio would be necessary. Of greater value would be extraction of $u^K$ alone, thereby avoiding inference from the ratio: currently, the data-based form of $u^K$ is materially influenced by results for $u^\pi$.