Kinematical correlations of dielectrons from semileptonic decays of heavy mesons and Drell-Yan processes at BNL RHIC

Abstract

We discuss kinematical correlations between charged leptons from semileptonic decays of open charm/bottom, leptons produced in the Drell-Yan mechanism as well as some other mechanisms not included so far in the literature in proton-proton scattering at BNL RHIC. The distributions of charm and bottom quarks/antiquarks are calculated in the framework of the $k_t$-factorization approach. For this calculation we use the Kwieciński unintegrated parton distributions. The hadronization of heavy quarks is done by means of Peterson et al. fragmentation function. We use semileptonic decay functions found by fitting recent semileptonic data obtained by the CLEO and BABAR collaborations. The Drell-Yan processes were calculated including transverse momenta of quarks and antiquarks, also using the Kwieciński parton distributions. We have also took into consideration reactions initiated by purely QED $γ^*γ^*$-fusion in elastic and inelastic pp collisions as well as recently proposed diffractive mechanism of exclusive charm-anticharm production. The contribution of the later mechanism is rather small. We get good description of the dilepton invariant mass spectrum measured recently by the PHENIX collaboration and present predictions for the dilepton pair transverse momentum distribution as well as distribution in azimuthal angle between electron and positron.