Single spin asymmetry in heavy flavor photoproduction as a test of pQCD

We analyze in the framework of pQCD the properties of the single spin asymm etry in heavy flavor production by linearly polarized photons. At leading o rder, the parallel-perpendicular asymmetry in azimuthal distributions of bo th charm and bottom quark is predicted to be about 20% in a wide region of initial energy. Our analysis shows that the next-to-leading order correctio ns practically do nor affect the Born predictions for the azimuthal asymmet ry at energies of the fixed target experiments. Both lending and next-to-le ading order predictions for the asymmetry are insensitive to within few per cent to theoretical uncertainties in the QCD input parameters: m(Q), mu(R), mu(F), mu(F), Lambda(QCD) and in the gluon distribution function. We estim ate also nonperturbative contributions to azimuthal distributions due to th e gluon transverse motion in the target and the final quark fragmentation. Our calculations show that nonperturbative corrections to a B-meson azimuth al asymmetry are negligible. We conclude that measurements of the single sp in asymmetry would provide a good test of pQCD applicability ro heavy flavo r production at fixed target energies. (C) 2000 Elsevier Science B.V. All r ights reserved.