The production of D*+, D0, D+ , Ds+ and lambda_c+ charm hadrons and their antiparticles in e p 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 < 1 GeV2 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 momentum p_T(D,lambda_c) > 3.8 GeV and pseudorapidity eta(D,\Lambda_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, gamma_s, and the fraction of charged D mesons produced in a vector state. The measured Ru/d and gamma_s values agree with those obtained in deep inelastic scattering and in e + e- annihilations. The results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.
Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
COSTA, Marco;MONACO, Vincenzo;SACCHI, Roberto;SOLANO, Ada Maria;
2005-01-01
Abstract
The production of D*+, D0, D+ , Ds+ and lambda_c+ charm hadrons and their antiparticles in e p 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 < 1 GeV2 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 momentum p_T(D,lambda_c) > 3.8 GeV and pseudorapidity eta(D,\Lambda_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, gamma_s, and the fraction of charged D mesons produced in a vector state. The measured Ru/d and gamma_s values agree with those obtained in deep inelastic scattering and in e + e- annihilations. The results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.File | Dimensione | Formato | |
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