Charm at HERA I and HERA II with the ZEUS experiment
Inclusive jet cross sections in photoproduction for events containing a D* meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb_1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2, and a photon-proton centre-of-mass energy in the range 130 < Wlp < 280 GeV. The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) predictions which incorporate leading-order matrix elements, followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where extra parton radiation is present. The MC models give a better description of the shape of the measured cross sections. This thesis ends with a look at the first HERA II data. The decay of D mesons were studied and for the first time the newly installed micro vertex detector (MVD) was used to tag charm mesons using secondary vertices arising from the decay of (c * D or b * c * D). This shows that the MVD will be a powerful tool in the future analyses of heavy quark production at ZEUS.