NLO corrections and contribution of a tensor gluon operator to the process #gamma#~*#gamma# -> #pi##pi#

摘要

We have calculated the NLO corrections for the leading twist amplitude of the reaction #gamma#~*#gamma# -> #pi##pi# at large virtuality of the photon and at W~2 Q~2. With a simple model for the two-pion quark and gluon distribution amplitudes we have estimated that the NLO effects may reduce the leading-order amplitude by as much as 30%. We have found that besides the usual twist-2 quark and gluon operators the NLO amplitude receives contribution from a distribution associated with twist-2 tensor gluon operator. The new gluon distribution can be investigated by studying the azimuthal asymmetry of the cross section for e + #gamma# -> e' + #pi##pi#.