Single Spin Asymmetry in Heavy Quark Photoproduction (and Decay) as a Test of PQCD

Abstract

In the framework of perturbative QCD, the basic spin-averaged characteristics of heavy flavor hadro-, photo- and electroproduction are known exactly up to the next-to-leading order (NLO). During the last ten years, these NLO results have been widely used for a phenomenological description of available data (for a review see [1]). At the same time, the key question still remains open: How to test the applicability of QCD at fixed order to the heavy quark production? The problem is twofold. On the one hand, the NLO corrections are large; they increase the leading order (LO) predictions for both charm and bottom production cross sections approximately by a factor of two. For this reason, one could expect that higher-order corrections, as well as nonperturbative contributions, can be essential in these processes, especially for the c-quark case. On the other hand, it is very difficult to compare directly, without additional assumptions, pQCD predictions for spin-averaged cross sections with experimental data because of a high sensivity of the theoretical calculations to standard uncertainties in the input QCD parameters: m _Q, the factorization and renormalization scales, μ _F and μ _R , Λ _QCD and the parton distribution functions [2, 3].