Uncertainties in pion and kaon fragmentation functions

TL;DR

This paper assesses uncertainties in parton-to-pion and kaon fragmentation functions using global QCD analyses, validating the Hessian method against the Lagrange multiplier approach and providing eigenvector sets for practical uncertainty propagation.

Contribution

It introduces validated uncertainty estimates for fragmentation functions and compares two methods, offering tools for broader application in particle physics analyses.

Findings

Hessian and Lagrange multiplier methods produce consistent uncertainty estimates.

Eigenvector sets enable easy propagation of uncertainties to observables.

Validated fragmentation functions improve predictions for hadron production processes.

Abstract

We present a detailed assessment of uncertainties in parton-to-pion and parton-to-kaon fragmentation functions obtained in recent global QCD analyses of single-inclusive hadron production data at next-to-leading order accuracy. We use the robust Lagrange multiplier approach for determining uncertainties to validate the applicability of the simpler but approximate Hessian method. Extensive comparisons of the results obtained within both methods are presented for the individual parton-to-pion and kaon fragmentation functions. We provide Hessian eigenvector sets of pion and kaon fragmentation functions that allow one to easily propagate their uncertainties to any observable. Various applications of these sets are presented for pion and kaon production in electron-positron annihilation, lepton-nucleon scattering, and proton-proton collisions.