No abstract

The invariant cross sections for direct photon production in hadron-hadron collisions are calculated for several initial energies (SPS, ISR, SppS, RHIC, Tevatron, LHC) including initial parton transverse momenta within the formalism of unintegrated parton distributions (UPDF). Different approaches from the literature are compared and discussed. A special emphasis is put on the Kimber-MartinRyskin (KMR) distributions and their extension into the soft region. Sum rules for UPDFs are formulated and discussed in detail. We find a violation of naive number sum rules for the KMR UPDFs. An interesting interplay of perturbative (large k 2 t ) and nonperturbative (small k 2 t ) regions of UPDFs in the production of both soft and hard photons is identified. The kt-factorization approach with the KMR UPDFs is inconsistent with the collinear approach at large transverse momenta of photons. Kwieciński UPDFs provide very good description of all world data, especially at SPS and ISR energies. Off-shell effects are discussed and quantified. Predictions for the CERN LHC are given. Very forward/backward regions in rapidity at LHC energy are discussed and a possibility to test unintegrated gluon distributions (UGDF) is presented.

We extend the Golec-Biernat-Wüsthoff model for virtual photonproton scattering to include the resolved photon component explicitly. The parameters of the resolved photon component are taken from the literature, while the parameters of the dipole-nucleon interaction are fitted to the HERA data in a selected limited range of x and Q 2 . A good agreement with experimental data is obtained far beyond the region of the fit.

The invariant cross sections for direct photon production in hadron-hadron collisions are calculated for several initial energies (SPS, ISR, SppS, 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 longstanding problem of understanding the low energy and low transverse momentum data.

We compare results of k t-factorization approach and next-to-leading order collinear-factorization approach for photon-jet correlations in pp and pp collisions at RHIC, Tevatron and LHC energies. We discuss correlations in azimuthal angle as well as in two-dimensional space of transverse momenta of photon and jet. Different unintegrated parton distributions (UPDF) are included in the k t-factorization approach. The results depend on UPDFs used. The results of NLO collinearfactorization are shown for comparison.