Direct Photon Production in $pp$ and $p\bar{p}$ Collisions at High Energies

Abstract

The invariant cross sections for direct photon production in hadron-hadron collisions are calculated for several initial energies (SPS, ISR, S$p\bar{p}$S, RHIC, Tevatron, LHC) including initial parton transverse momenta within the formalism of unintegrated parton distributions (UPDF). Kwieciński UPDFs provide very good description of all world data, especially at SPS and ISR energies. Inclusion of the QCD evolution effects and especially their effect on initial parton transverse momenta allowed to solve the long-standing problem of understanding the low energy and low transverse momentum data.

Comments: presented at the international conference MESON2006, Cracow 5 pages, 3 figures