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Measurement of Charm Fragmentation Ratios and Fractions in Photoproduction at HERA
Journal article   Peer reviewed

Measurement of Charm Fragmentation Ratios and Fractions in Photoproduction at HERA

ZEUS Collaboration and Jose Repond
The European Physical Journal C , Vol.44, pp.351-366
2005
DOI: 10.1140/epjc/s2005-02397-3
url
https://arxiv.org/pdf/hep-ex/0508019View
Open Access

Abstract

The production of D∗+, D0, D+, D+s and Λ+c charm hadrons and their antiparticles in ep scattering at HERA was measured with the ZEUS detector using an integrated luminosity of 79 pb−1. 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<W < 300 GeV. The charm hadrons were reconstructed in the range of transverse momentumpT (D,Λc) > 3.8GeV and pseudorapidity |η(D,Λc)| < 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, γs, and the fraction of charged D mesons produced in a vector state, Pdv. The measured Ru/d and γs 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, Λc), 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 → Λ+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.

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