Charm-quark fragmentation with an effective coupling constant

TL;DR

This paper introduces a non-perturbative model using an effective coupling constant to describe charm-quark fragmentation in e+e- annihilation, successfully fitting some experimental data and moments but with notable discrepancies and uncertainties.

Contribution

It presents a parameter-free, non-perturbative model based on an effective coupling constant for charm-quark fragmentation, extending the theoretical framework with NNLO and NNLL calculations.

Findings

Reasonable fit to ALEPH D*+- spectra for x<1-Lambda/m_c

Reproduces first ten Mellin moments of various data sets

Large theoretical uncertainties highlight need for full NNLO/NNLL analysis

Abstract

We use a recently proposed non-perturbative model, based on an effective strong coupling constant and free from tunable parameters, to study c-flavoured hadron production in e+e- annihilation. Charm-quark production is described in the framework of perturbative fragmentation functions, with NLO coefficient functions, NLL non-singlet DGLAP evolution and NNLL large-x resummation. We model hadronization effects by means of the effective coupling constant in the NNLO approximation and compare our results with experimental data taken at the Z0 pole and at the Upsilon(4S) resonance. We find that, within the experimental and theoretical uncertainties, our model is able to give a reasonable description of D*+-meson spectra from ALEPH for x<1-Lambda/m_c. More serious discrepancies are instead present when comparing with D and D^* data from BELLE and CLEO in x-space. Within the errors, our model is nonetheless capable of reproducing the first ten Mellin moments of all considered data sets. However, the fairly large theoretical uncertainties call for a full NNLO/NNLL analysis.