Reexamining charm versus bottom quark energy loss inside a color-deconfined medium

TL;DR

This paper re-examines the energy loss mechanisms of charm and bottom quarks in a quark-gluon plasma, revealing that heavier quarks can experience stronger interactions through string potentials, leading to different energy loss patterns at various momenta.

Contribution

It introduces a linear Boltzmann transport model incorporating both Yukawa and string interactions, showing mass-dependent energy loss behaviors that challenge traditional assumptions.

Findings

Heavier quarks can have stronger string potential scatterings.

Bottom quarks show less energy loss than charm at low pT, opposite at high pT.

Predicted transport coefficients differ between bottom and charm quarks.

Abstract

The general intuition that heavier partons suffer weaker energy loss inside a quark-gluon plasma (QGP) medium is critically re-examined. Within a linear Boltzmann transport model that includes both Yukawa and string types of interactions between heavy quarks and the QGP, we find that while the radiative energy loss is suppressed by the parton mass, heavier partons can experience stronger string potential scatterings with the medium. Their competition may result in less energy loss of bottom quarks than charm quarks at low transverse momentum ($p_\mathrm{T}$) but an inverse order at high $p_\mathrm{T}$. Our model calculation shows a weaker nuclear modification on bottom particles than charm particles at low $p_\mathrm{T}$, as observed by both RHIC and LHC experiments, but predicts an opposite hierarchy at high $p_\mathrm{T}$. A larger momentum space transport coefficient ($\hat{q}$) and a smaller spatial diffusion coefficient ($D_\mathrm{s}$) are found for bottom quarks than for charm quarks.