Measurement of charm fragmentation ratios and fractions in photoproduction at HERA

The ZEUS collaboration

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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, Pd v. The measured Ru/d and γs values agree with those obtained in deep inelastic scattering and in e+e- annihilations. The measured Pd v 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.

Original languageEnglish
Pages (from-to)351-366
Number of pages16
JournalEuropean Physical Journal C
Issue number3
StatePublished - 2005


FundersFunder number
Belgian Federal Science Policy Office 1 Hereafter
Italian National Institute for Nuclear Physics
Korean Ministry of Education and Korea Science and Engineering Foundation
MINERVA Gesellschaft für Forschung GmbH
Max Planck Institute
Netherlands Foundation for Research on Matter
Polish Ministry of Scientific Research and Information Technology112/E-356/SPUB/DESY/P-03/DZ 116/2003–2005, 2P03B 12625 7, 1 P03B 065 27
National Science Foundation
U.S. Department of Energy
Baylor University
Hawai`i Educational Research Association
Natural Sciences and Engineering Research Council of Canada
Deutsches Elektronen-Synchrotron
Ministry of Education, Culture, Sports, Science and Technology
Stichting voor Fundamenteel Onderzoek der Materie
German-Israeli Foundation for Scientific Research and Development
United States-Israel Binational Science Foundation
Bundesministerium für Bildung und ForschungHZ1GUA 2, N 1685.2003.2
Bundesministerium für Bildung und Forschung
Fonds De La Recherche Scientifique - FNRS
Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture
Ministerio de Educación, Cultura y Deporte
Ministry of Education and Science of the Russian Federation
Israel Science Foundation293/02-11.2
Israel Science Foundation
Instituto Nazionale di Fisica Nucleare
University of Tokyo
Universität Hamburg
Komitet Badań Naukowych620/E-77/SPB/DESY/P-03/DZ 117/2003– 2005
Komitet Badań Naukowych
Comisión Interministerial de Ciencia y Tecnología
Korle-Bu Neuroscience Foundation2P03B12725, 2P03B12925 29
Korle-Bu Neuroscience Foundation
Lomonosov Moscow State University


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