Photon-jet correlations in $pp$ and $p \bar p$ collisions

Abstract

We compare results of the $k_t$-factorization approach and the next-to-leading order collinear-factorization approach for photon-jet correlations in $pp$ and $p \bar p$ collisions at RHIC and Tevatron energies. We discuss correlations in the azimuthal angle as well as in the two-dimensional space of transverse momentum of photon and jet. Different unintegrated parton distributions (UPDF) are included in the $k_t$-factorization approach. The results depend on UPDFs used. The standard collinear approach gives cross section comparable to the $k_t$-factorization approach. For correlations of the photon and any jet the NLO contributions dominate at relatively small azimuthal angles as well as for asymmetric transverse momenta. For correlations of the photon with the leading jet (the one having the biggest transverse momentum) the NLO approach gives zero contribution at $\phi_{-} < \pi/2$ which opens a possibility to study higher-order terms and/or UPDFs in this region.