1996/06/26 by E. M. Levin, A. D. Martin, M. G. Ryskin +1 · 1 citation
Physics and Astronomy · #hep-ph
published as Z.Phys. C74 (1997) 671-685 · 34 pages, LaTeX, 15 Postscript figures included using epsf. The complete paper, including figures, is also available via anonymous ftp at ftp://cpt1.dur.ac.uk/pub/preprints/dtp96/dtp9650/
arxiv created 1996/06/26 · arxiv updated 2009/11/30
We use perturbative QCD to calculate the cross sections σL,T for the diffractive production of open charm (cc) from longitudinally and transversely polarised photons (of virtuality Q2) incident at high energy (√(s)) on a proton target. We study both the Q2 and M2 dependence of the cross sections, where M is the invariant mass of the cc pair. Surprisingly, the result for σT, as well as for σL, is perturbatively stable. We estimate higher-order corrections and find a sizeable enhancement of the cross sections. The cross sections depend on the \it square of the gluon density g (x, K2), and we show that the observation of open charm at the HERA electron-proton collider can act as a sensitive probe of the gluon distribution for x = (Q2 + M2)/s and scale K2 = (mc2 + ⟨ kT2 ⟩) (1 + Q2/M2) where the average quark transverse momentum squared ⟨ kT2 ⟩ ∼ mc2. As compared to diffractive J/ψ production, open charm has the advantage that it is independent of the non-perturbative ambiguities arising from the J/ψ wave function. We estimate the fraction of diffractive events that arise from cc production.