Measurement of charm fragmentation ratios and fractionsin photoproduction at HERA
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2005, Springer New York LLC. All rights reserved. The production of D+, D0, D+, D+s and +c charm hadrons and their antiparticles in ep scattering at HERA was measured with the ZEUS detector using an integrated luminosity of 79 pb1. The measurement has been performed in the photoproduction regime with the exchanged-photon virtuality Q2 < 1GeV2 and for photon-proton centre-of-mass energies in the range 130 3.8GeV and pseudorapidity |(D,c)| < 1.6. The production cross sections were used to determine the ratio of neutral and charged D-meson production rates, Ru/d, the strangeness-suppression factor, s, and the fraction of charged D mesons produced in a vector state, Pdv. The measured Ru/d and s values agree with those obtained in deep inelastic scattering and in e+e- annihilations. The measured Pdv value is smaller than, but consistent with, the previous measurements. The fractions of c quarks hadronising as a particular charm hadron, f(c D, c), were derived in the given kinematic range. The measured open-charm fragmentation fractions are consistent with previous results, although the measured f(c D*+) is smaller and f(c +c) is larger than those obtained in e+e- annihilations. These results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.
