Pion and Kaon Fragmentation Functions from Continuum Schwinger Function Methods

TL;DR

This paper derives pion and kaon fragmentation functions from their distribution functions using continuum Schwinger methods, providing predictions consistent with QCD and revealing symmetry breaking effects in high energy reactions.

Contribution

It introduces a novel approach to obtain fragmentation functions from distribution functions via the Drell-Levy-Yan relation within continuum Schwinger methods, advancing understanding of hadron production.

Findings

FFs satisfy QCD endpoint behavior

SU(3) symmetry breaking observed in kaon ratios

Pion/kaon ratio approaches a mass-independent limit

Abstract

Using the Drell-Levy-Yan relation, the pion and kaon elementary fragmentation functions (EFFs) are obtained from their hadron-scale parton distribution functions (DFs). These EFFs serve as driving terms in the hadron cascade equations, whose solution yields the complete array of hadron-scale fragmentation functions (FFs) for pion and kaon production in high energy reactions. Evolved to experimental scales, the continuum Schwinger function methods (CSMs) predictions satisfy QCD endpoint behavior: nonsinglet FFs vanish at $z=0$, singlet FFs diverge faster than $1/z$. Jet multiplicity predictions reveal SU(3) symmetry breaking in the charged/neutral kaon ratio, decreasing with energy, and show the pion/kaon ratio in $e^+e^-$ collisions asymptotes to a mass-independent value.