Measurement of charm fragmentation fractions in photoproduction at HERA

TL;DR

This paper measures how charm quarks transform into specific charm hadrons in photoproduction at HERA, providing insights into fragmentation processes and comparing results with previous experiments to test process independence.

Contribution

It provides new measurements of charm fragmentation fractions in photoproduction and compares them with e+e- results to support process independence of fragmentation.

Findings

Fragmentation fractions are consistent with previous HERA and e+e- results.

The data support the hypothesis that fragmentation is process-independent.

Measured ratios and suppression factors align with theoretical expectations.

Abstract

The production of D^0, D^*+, D^+, D_s+ and Lambda_c^+ charm hadrons and their antiparticles in ep scattering at HERA has been studied with the ZEUS detector, using a total integrated luminosity of 372 pb^-1. The fractions of charm quarks hadronising into a particular charm hadron were derived. In addition, the ratio of neutral to charged D-meson production rates, the fraction of charged D mesons produced in a vector state, and the stangeness-suppression factor have been determined. The measurements have been performed in the photoproduction regime. The charm hadrons were reconstructed in the range of transverse momentum p_T >3.8 GeV and pseudorapidity |eta|<1.6. The charm fragmentation fractions are compared to previous results from HERA and from e+e-experiments. The data support the hypothesis that fragmentation is independent of the production process.