Single Spin Asymmetry in Heavy Flavor Photoproduction as a Test of pQCD

TL;DR

This paper predicts a significant single spin asymmetry in heavy flavor photoproduction using pQCD, showing it is stable against higher-order corrections and uncertainties, making it a good test for pQCD at fixed target energies.

Contribution

The study provides leading and next-to-leading order predictions for azimuthal asymmetry in heavy flavor production, demonstrating their stability and negligible nonperturbative effects.

Findings

Asymmetry predicted to be about 20% at leading order.

Next-to-leading order corrections do not significantly alter predictions.

Nonperturbative effects are negligible for B-meson asymmetry.

Abstract

We analyze in the framework of pQCD the properties of the single spin asymmetry in heavy flavor production by linearly polarized photons. At leading order, the parallel- perpendicular asymmetry in azimuthal distributions of both 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 corrections practically do not affect the Born predictions for the azimuthal asymmetry at energies of the fixed target experiments. Both leading and next-to-leading order predictions for the asymmetry are insensitive to within few percent to theoretical uncertainties in the QCD input parameters: $m_{Q}$, $\mu_{R}$, $\mu_{F}$, $\Lambda_{QCD}$ and in the gluon distribution function. We estimate also nonperturbative contributions to azimuthal distributions due to the gluon transverse motion in the target and the final quark fragmentation. Our calculations show that nonperturbative corrections to a $B$-meson azimuthal asymmetry are negligible. We conclude that measurements of the single spin asymmetry would provide a good test of pQCD applicability to heavy flavor production at fixed target energies.