Production of Heavy Flavours with Associated Jets at HERA

Abstract

Inclusive cross-sections for the production of open beauty and charm in ep collisions at HERA recorded with the ZEUS detector in the years 1996-2000 are measured. The data is restricted to photoproduction processes, i.e. collision events with small four-momentum transfers squared, Q²~0. Two associated jets with transverse energies E_t7(6) GeV and pseudo-rapidities |η|<2.5 are required. The flavour is tagged by the identification of electrons and positrons from semi-leptonic decays of the heavy quark. For this a likelihood method is developed, mainly consisting of energy loss measurements in the central drift chamber of the detector and some other discriminant variables. The fractions of beauty and charm production are determined by a fit of Monte Carlo templates to the data. The total measured production cross-section for bb¯ production is 820±150⁺²⁰_-30 pb for centre-of-mass energies vs_ep=300 GeV and 1170±130⁺³⁰_-100 pb for vs_ep=318 GeV. The total cross-section for charm production is given as well as differential cross-sections for bb¯ and cc¯ production.