Effects of Parton kt in High-pt Particle Production

Abstract

We report on recent work concerning the phenomenology of initial-state parton-kt effects in direct-photon production and related processes in hadron collisions. After a brief summary of a kt-smearing model, we present a study of recent results on fixed-target and collider direct-photon production, using complementary data on diphoton and pion production that provide empirical guidance on the required amount of kt broadening. This approach provides a consistent description of the observed deviations of next-to-leading order QCD calculations relative to the inclusive direct-photon and pizero data. We also comment on the implications of these results for the extraction of the gluon distribution of the nucleon.

Comments: Talk given at Hadron Structure '98, Stara Lesna, September 7-13, 1998; to be published in the conference Proceedings. The submission contains a LaTeX source file for the text of the paper, two style files (hsproc.sty and art10.sty) and 11 postscript files with figures; the package is tarred, gzipped and uuencoded (and can be unpacked on a Unix system by "csh file.uu")