Charm production in deep inelastic and diffractive scattering.pdf

a r X i v : h e p - p h / 9 7 0 4 2 0 3 v 1 1 A p r 1 9 9 7 NIKHEF 97–015 hep-ph/9704203 Charm production in deep inelastic and diffractive scattering L.P.A. Haakman a, A.B. Kaidalov b, J.H. Koch a a National Institute for Nuclear Physics and High Energy Physics (NIKHEF), P.O. Box 41882, NL-1009 DB Amsterdam, The Netherlands b Institute of Theoretical and Experimental Physics, B. Cheremushinskaya 25, 117 259 Moscow, Russia (March 1997) We consider the production of charm by real and virtual photons. Special attention is paid to diffractive charm production, which provides information on the gluonic content of the Pomeron. Our calculations are based on the gluon distributions of the CKMT-model, which is shown to lead to agreement with the data on open charm production in deep inelastic scattering. We compare predictions for diffractive charm production of different models for the distribution of gluons in the Pomeron. Experiments at HERA should be able to discriminate between them. Predictions for beauty production in diffractive and non-diffractive interactions of photons are also given. I. INTRODUCTION The production of heavy quarks in deep inelastic electron scattering from a proton has received increasing attention recently, since this reaction is seen as a tool to probe the gluon distribution in the nucleon. Due to the large mass of the quark, the reaction is believed to be driven by a perturbative mechanism, photon-gluon fusion, and is therefore sensitive to the nucleonic gluon density. We consider here in a consistent way the production of charm in deep inelastic scattering (DIS) as well as in hard diffractive scattering. The latter process, while driven by the same basic reaction mechanism, probes a different gluon density. As the diffractive processes are mostly seen as mediated by the Pomeron exchange, the relevant quantity in diffractive production is then the gluon distribution in the Pomeron; a review can be found in Ref. [1]. The distribution of gl