An Analysis on the Parton Distribution Functions of Heavy Mesons

Abstract

In this work, we investigate the constituent parton distribution functions (PDFs) of the kaon and heavy pseudoscalar mesons within the light-cone quark model. Starting from the initial-scale quark and antiquark PDFs, obtained by evaluating the quark--quark correlation functions for individual mesons, we perform quantum chromodynamics (QCD) evolution to determine their partonic structure at higher energy scales. The QCD evolution is carried out using the next-to-leading-order (NLO) Dokshitzer--Gribov--Lipatov--Altarelli--Parisi (DGLAP) equations. We further compute the average longitudinal momentum fractions carried by the individual constituents at both the model and evolved scales. In addition, we predict the NLO structure functions of the kaon at energy scales relevant to the upcoming Electron--Ion Collider (EIC). For the COMPASS++/AMBER experiment, we also present detailed predictions for the NLO Drell--Yan cross sections induced by both $K^{+}$ and $K^{-}$ beams, using carbon, tungsten, and aluminum as nuclear targets. Finally, we demonstrate the dominance of the heavier constituents over the lighter constituents in heavy mesons in terms of the momentum fractions they carry.

Comments: Accepted for Publication in PRD