Study of Charm Fragmentation into D^{*\pm} Mesons in Deep-Inelastic Scattering at HERA
H1 Collaboration
TL;DR
This study investigates how charm quarks fragment into D*± mesons in deep-inelastic scattering at HERA by measuring normalised differential cross sections as functions of two fragmentation-sensitive observables, z_hem and z_jet, in two event samples (with and without a D* jet). It compares LO and NLO QCD predictions from RAPGAP, CASCADE, and HVQDIS, using several fragmentation functions (Peterson, Kartvelishvili, Bowler) within Lund string hadronization, and extracts fragmentation-parameter values via a reweighting procedure. The results show generally good agreement between data and models, with Kartvelishvili fragmentation often preferred; the Peterson function can fail for NLO HVQDIS, and the no-jet, near-threshold region reveals significant tensions that indicate limitations of current fragmentation implementations. Overall, the findings support fragmentation-function universality under standard modeling choices, while highlighting threshold-region challenges that motivate further theoretical refinement.
Abstract
The process of charm quark fragmentation is studied using $D^{*\pm}$ meson production in deep-inelastic scattering as measured by the H1 detector at HERA. Two different regions of phase space are investigated defined by the presence or absence of a jet containing the $D^{*\pm}$ meson in the event. The parameters of fragmentation functions are extracted for QCD models based on leading order matrix elements and DGLAP or CCFM evolution of partons together with string fragmentation and particle decays. Additionally, they are determined for a next-to-leading order QCD calculation in the fixed flavour number scheme using the independent fragmentation of charm quarks to $D^{*\pm}$ mesons.