Production of leptons from decay of heavy-flavor hadrons in high-energy nuclear collisions

TL;DR

This study models heavy-flavor lepton production in high-energy nuclear collisions, analyzing various effects like energy loss, hadronization, and initial spectra, and compares suppression patterns across different collision systems.

Contribution

It introduces a comprehensive method to disentangle multiple factors influencing heavy-flavor lepton yields and provides insights into their relative importance at different transverse momenta.

Findings

Coalescence and decay channels significantly affect low-$p_T$ leptons.

Mass-dependent energy loss dominates at high-$p_T$.

Smaller suppression in Xe+Xe compared to Pb+Pb aligns with experimental data.

Abstract

This paper presents a theoretical study on the production of the heavy-flavour decay lepton (HFL) in high-energy nuclear collisions at the LHC. The pp-baseline is calculated by the FONLL program, which matches the next-to-leading order pQCD calculation with the next-to-leading-log large-$p_T$ resummation. The in-medium propagation of heavy quarks is driven by the modified Langevin equations, which consider both the elastic and inelastic partonic interactions. We propose a method to separate the respective influence of the six factors, such as pp-spectra, the cold nuclear matter (CNM) effects, in-medium energy loss (E-loss), fragmentation functions (FFs), coalescence (Coal), and decay channels, which may contribute to the larger $R_{AA}$ of HFL $\leftarrow b$ compared to that of HFL $\leftarrow c$ in nucleus-nucleus collisions. Based on quantitative analysis, we demonstrate that both coalescence hadronization, decay channels and the mass-dependent E-loss play an essential role at $p_T<5$ GeV, while the latter dominates the higher $p_T$ region. It is also found that the influences of the CNM effects and FFs are insignificant. At the same time, different initial pp-spectra of charm and bottom quarks have a considerable impact at $p_T>5$ GeV. Furthermore, we explore the path-length dependence of jet quenching by comparing the HFL $R_{AA}$ in two different collision systems. Our investigations show smaller HFL $R_{AA}$ in Pb+Pb than in Xe+Xe within the same centrality bin, consistent with the ALICE data. The longer propagation time and more effective energy loss of heavy quarks in Pb+Pb collisions play critical roles in the stronger yield suppression of the HFL compared to that in Xe+Xe. In addition, we observe a scaling behavior of the HFL $R_{AA}$ in Xe+Xe and Pb+Pb collisions.