EFFECTS OF PARTON INTRINSIC TRANSVERSE-MOMENTUM ON PHOTON PRODUCTION IN HARD-SCATTERING PROCESSES

We calculate the photon production cross section arising from the hard scattering of partons in nucleon-nucleon collisions by taking into ac count the intrinsic parton transverse momentum distribution and the ne xt-to-leading-order contributions. As first pointed out by Owens, the inclusion of the intrinsic transverse momentum distribution of partons leads to an enhancement of photon production cross section in the reg ion of photon transverse momenta of a few GeV/c for nucleon-nucleon co llisions at a center-of-mass energy of a few tens of GeV. The enhancem ent increases as root s decreases. Such an enhancement is an important consideration in the region of photon momenta under investigation in high-energy heavy-ion collisions.