Gluon density determination from open charm events at HERA

We study some prospects of measuring the gluon density in the proton using charm events at HERA for the ep center of mass energy √s = 314 GeV. We invoke the QCD-improved boson-gluon fusion model and find the following cross-section: σ(ep) → ecanti cX) ≅ O(0.6 μb). This cross-section would provide O(108) events/year, for an integrated luminosity of 100 pb-1. We have investigated two traditional methods for tagging of charm, namely, D*± reconstruction using the process D*± → D0 π± → (K--+π±)π±, an dileptonic decays of charmed hadrons (canti c → l+l-X). The inclusive cross-sections after full detector simulation are 103 pb and 102, respectively. In both cases the background was strongly reduced. By using these events, the gluon distribution in the proton can be measured in the range 10-3 ≤ χg ≤ 10-1. WE conclude that an adequate discrimination among the present theoretical parametrizations can be achieved at HERA. (orig.)