Dijet correlations at BNL RHIC: Leading-orderkt-factorization approach versus next-to-leading order collinear approach

Abstract

We compare results of the k{sub t}-factorization approach and the next-to-leading-order collinear-factorization approach for dijet correlations in proton-proton collisions at RHIC energies. We discuss correlations in azimuthal angle as well as correlations in two-dimensional space of transverse momenta of two jets. Some k{sub t}-factorization subprocesses are included for the first time in the literature. Different unintegrated gluon/parton distributions are used in the k{sub t}-factorization approach. The results depend on unintegrated gluon distribution functions (UGDF)/unintegrated parton distribution function (UPDF) used. For the collinear next-to-leading order (NLO) case, the situation depends significantly on whether we consider correlations of any two jets or correlations of leading jets only. In the first case, the 2{yields}2 contributions associated with soft radiations summed up in the k{sub t}-factorization approach dominate at {phi}{approx}{pi} and at equal moduli of jet transverse momenta. The collinear NLO 2{yields}3 contributions dominate over k{sub t}-factorization cross section at small relative azimuthal angles as well as for asymmetric transverse-momentum configurations. In the second case, the NLO contributions vanish at small relative azimuthal angles and/or large jet transverse-momentum disbalance due to simple kinematical constraints. There are no such limitations for the k{sub t}-factorization approach. All this makes the two approaches rather complementary. The rolemore » of several cuts is discussed and quantified.« less