# Effects of drag induced radiation and multi-stage evolution on heavy quark energy loss

## TL;DR

This paper introduces a multi-stage model for heavy quark energy loss in the quark-gluon plasma, highlighting the significant role of drag-induced radiation, and compares predictions with LHC experimental data.

## Contribution

It develops a novel multi-stage evolution framework for heavy quarks in QGP, incorporating both transverse and longitudinal transport coefficients, and couples it with hydrodynamics for quantitative analysis.

## Key findings

- Drag induced radiation significantly affects beauty quark energy loss.
- The model predicts increased B meson suppression and reduced B/D meson R_AA differences.
- Results align with LHC experimental observations.

## Abstract

Heavy quarks serve as ideal probes of the QGP properties produced in energetic nuclear collisions, and provide a unique opportunity to study the mass effects on parton energy loss. We develop a multi-stage approach for heavy quark evolution inside the QGP, in which heavy quarks first undergo a rare-scattering multiple-emission evolution at momenta large compared to their mass (sensitive only to the transverse diffusion coefficient $\hat{q}$ ), and then evolve through a single-scattering induced emission (Gunion-Bertsch) stage at momenta comparable to their mass [sensitive to not only $\hat{q}$, but also the longitudinal drag $\hat{e}$ and diffusion $\hat{e}_2$ coefficients]. This multi-stage approach is coupled to a (2+1)-D viscous hydrodynamic model for a quantitative investigation of charm vs. beauty quark energy loss inside the QGP. Based on this approach, we find that drag induced radiation has a considerable impact on the energy loss of intermediate $p_T$ massive beauty quarks. This effect increases the suppression of B mesons and narrows the difference between the $R_{AA}$ of B and D mesons. Our results are consistent with the experimental data at the LHC and contribute to a more quantitative understanding of the transverse momentum dependence of the mass hierarchy of parton energy loss inside the QGP.