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Predictions for D^*+- Photoproduction at HERA with New Fragmentation Functions from LEP1

J. Binnewies, B. A. Kniehl, G. Kramer

TL;DR

This work derives nonperturbative fragmentation functions for D^*± mesons by fitting LEP1 $e^+e^-$ data within a pure $MSbar$ scheme with five massless flavors, using Peterson charm FF and a bottom FF form. The resulting LO and NLO FF sets are then used to predict inclusive D^*± photoproduction in ep collisions at HERA, achieving good agreement with ZEUS data and demonstrating universality of FFs across reactions. The approach avoids prior issues of unphysical high-$x$ behavior seen in earlier schemes and shows perturbative stability between LO and NLO, though photon-PDF uncertainties remain a major theoretical limit, especially in forward kinematics. The study supports applying universal, nonperturbative FFs to high-energy processes and highlights areas where additional high-$p_T$ data could further test the framework.

Abstract

We present new sets of nonperturbative fragmentation functions for D^*+- mesons, both at leading and next-to-leading order in the MS-bar factorization scheme with five massless quark flavors. They are determined by fitting the latest OPAL and ALEPH data on inclusive D^*+- production in e^+e^- annihilation. We take the charm-quark fragmentation function to be of the form proposed by Peterson et al. and thus obtain new values of the epsilon_c parameter, which are specific for our choice of factorization scheme. With these fragmentation functions, recent data on inclusive D^*+- photoproduction in ep collisions at HERA are reasonably well reproduced.

Predictions for D^*+- Photoproduction at HERA with New Fragmentation Functions from LEP1

TL;DR

This work derives nonperturbative fragmentation functions for D^*± mesons by fitting LEP1 data within a pure scheme with five massless flavors, using Peterson charm FF and a bottom FF form. The resulting LO and NLO FF sets are then used to predict inclusive D^*± photoproduction in ep collisions at HERA, achieving good agreement with ZEUS data and demonstrating universality of FFs across reactions. The approach avoids prior issues of unphysical high- behavior seen in earlier schemes and shows perturbative stability between LO and NLO, though photon-PDF uncertainties remain a major theoretical limit, especially in forward kinematics. The study supports applying universal, nonperturbative FFs to high-energy processes and highlights areas where additional high- data could further test the framework.

Abstract

We present new sets of nonperturbative fragmentation functions for D^*+- mesons, both at leading and next-to-leading order in the MS-bar factorization scheme with five massless quark flavors. They are determined by fitting the latest OPAL and ALEPH data on inclusive D^*+- production in e^+e^- annihilation. We take the charm-quark fragmentation function to be of the form proposed by Peterson et al. and thus obtain new values of the epsilon_c parameter, which are specific for our choice of factorization scheme. With these fragmentation functions, recent data on inclusive D^*+- photoproduction in ep collisions at HERA are reasonably well reproduced.

Paper Structure

This paper contains 4 sections, 5 equations, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. $D^{*\pm}$ Production in $e^+e^-$ Annihilation
  3. $D^{*\pm}$ Production in Low-$Q^2$ $ep$ Collisions
  4. Conclusions

Figures (2)

  • Figure 1: (a) The cross sections of inclusive $D^{*\pm}$ production in $e^+e^-$ annihilation evaluated with sets LO O and NLO O are compared with the OPAL data 16. The three pairs of curves correspond to the $Z\to c\bar{c}$, $Z\to b\bar{b}$, and full samples. (b) The same for sets LO A and NLO A and the ALEPH data 17.
  • Figure :