Heavy quark mass effects in parton-to-kaon hadronization probabilities

Manuel Epele,Carlos García Canal,R Sassot

doi:10.1016/j.physletb.2018.11.069

Abstract

We examine the relevance of the heavy quarks masses in the perturbative QCD description of hard interactions where charged kaons are produced in the final state. We extract a set of parton-to-kaon hadronization probabilities from a next to leading order QCD global analysis where a general mass variable flavor number scheme accounting for mass effects is implemented. We compare the results with those obtained in the massless approximation and also with those found in the case of final state pions. At variance with the very significant improvement found for the much more precise pion fragmentation phenomenology, the heavy quark mass dependent scheme improves mildly the overall description of current kaon production data. Nevertheless, we find a noticeable reduction in the charm-to-kaon hadronization probability.

Highlights

Ultra-relativistic proton–proton collisions produce very large numbers of final particles, some of which emerge with transverse momentum of several GeV
In the context of perturbative Quantum Chromodynamics (QCD) [3], hard hadronic collisions with identified final state hadrons are described perturbatively in terms of effective hard scattering cross sections and two sets of universal nonperturbative functions: parton distributions (PDF), which describe the internal structure of the hadrons just before the interaction process, and fragmentation functions (FF) that encode the information about the hadronization processes [4]
Down and strange quarks, the same restriction that allows a perturbative treatment, i.e. energy scales much larger than 3QCD, guarantees the smallness of potential dynamical effects arising from their masses, making natural to treat them as massless, with the advantage of the all-order resummations implicit in massless parton approaches

Summary

Introduction

Ultra-relativistic proton–proton collisions produce very large numbers of final particles, some of which emerge with transverse momentum of several GeV. The largest fraction of this background in experiments such as those performed at the Large Hadron Collider [1] and at the Relativistic Heavy Ion Collider [2] are light hadrons, such as pions and kaons These are produced in the final state through the hadronization or fragmentation mechanism by which hard interacting partons evolve into a physical and intrinsically non-perturbative colorless hadronic state. In the context of perturbative Quantum Chromodynamics (QCD) [3], hard hadronic collisions with identified final state hadrons are described perturbatively in terms of effective hard scattering cross sections and two sets of universal nonperturbative functions: parton distributions (PDF), which describe the internal structure of the hadrons just before the interaction process, and fragmentation functions (FF) that encode the information about the hadronization processes [4] Because of their non perturbative nature, PDFs and FFs need to be extracted through QCD global analyses of experimental data, where the hard scattering cross sections are approximated with increasing precision [5,6]. At variance with the analysis performed using much more precise pion production data, we see only a mild improvement in the quality of the fit

Heavy quark into kaon fragmentation

GMVFN scheme global analysis

10 GeV2 and

Conclusions