Leptons from heavy-quark semileptonic decay in pA collisions within the CGC framework

TL;DR

This paper investigates lepton production from heavy-quark decays in proton-proton and proton-nucleus collisions at RHIC and LHC energies using the CGC framework, highlighting the role of gluon saturation effects.

Contribution

It introduces a CGC-based calculation of lepton spectra from heavy-flavor decays, incorporating the energy-dependent gluon distribution from the BK equation with running coupling.

Findings

Leptons at low transverse momentum mainly originate from gluon saturation effects.

The computed lepton spectra are slightly harder than experimental data.

Nuclear modification factors for J/ψ and D mesons are updated at LHC energies.

Abstract

We study single lepton production from semileptonic decays of heavy flavor hadrons ($D,B\rightarrow~l$) in pp and p$A$ collisions at RHIC and the LHC within the saturation/Color-Glass-Condensate (CGC) framework. Using the gluon distribution function obtained with the dipole amplitude, whose energy dependence is described by the Balitsky-Kovchegov equation with running coupling effect, we compute the transverse-momentum ($p_\perp$) spectra of the lepton yields at mid and forward rapidities. We find that a large fraction of leptons at low $p_\perp$ stems from the saturation regime of the incoming gluons in the target, especially in p$A$ collisions at the LHC. The resultant $p_\perp$ spectra is slightly harder than the data, but the nuclear modification factor seems consistent with the data within some uncertainty. We also update the nuclear modification factors for J/$\psi$ and $D$ meson at the LHC energy.