Heavy quark production at collider energies: some selected topics

TL;DR

This paper analyzes heavy quark production at collider energies, focusing on charm and bottom quarks, using various approaches to describe their distributions, hadronization, and decay, and compares results with experimental data from RHIC and PHENIX.

Contribution

It introduces a comprehensive approach combining $k_t$-factorization, phenomenological fragmentation, and decay functions to describe heavy quark production and decay in $pp$ collisions, including new mechanisms and correlations.

Findings

Good description of high transverse momentum electrons from charm/bottom decays.

Identified missing strength at small transverse momenta of electrons.

Achieved agreement with dilepton invariant mass spectra from PHENIX.

Abstract

We discuss production of charm quarks and mesons as well as nonphotonic electrons in $pp$ scattering at RHIC. The distributions in rapidity and transverse momentum of charm and bottom quarks/antiquarks are calculated in the $k_t$-factorization approach. The hadronization of heavy quarks is done by means of fenomenological fragmentation functions. The semileptonic decay functions found by fitting semileptonic decay data measured by the CLEO and BABAR collaborations are used. Good description of the inclusive data at large transverse momenta of electrons is obtained and a missing strength at small transverse momenta of electrons is found. Furthermore 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. When calculating the Drell-Yan processes we include transverse momenta of $q$ and $\bar q$, using the Kwieci\'nski parton distributions. Reactions initiated by purely QED $\gamma^*\gamma^*$-fusion in elastic and inelastic $pp$ collisions as well as diffractive mechanism of exclusive $c \bar c$ production are included. A good description of the dilepton invariant mass spectrum measured by the PHENIX collaboration is achieved. Predictions for the dilepton pair transverse momentum distribution as well as distribution in azimuthal angle between electron and positron are presented.