Towards an understanding of the RHIC single electron data

TL;DR

This paper investigates heavy quark energy loss in quark-gluon plasma using improved pQCD calculations, successfully matching experimental data on electron suppression and azimuthal anisotropy at RHIC.

Contribution

It introduces a running coupling and a realistic HTL-based infrared regulator, significantly enhancing collisional energy loss estimates in pQCD models.

Findings

Enhanced collisional energy loss aligns with experimental $R_{AA}$ and $v_2$ data.

Fixed coupling pQCD underestimates heavy quark energy loss.

Radiative energy loss may still contribute but is not excluded.

Abstract

High transverse momentum ($p_T$) single non-photonic electrons which have been measured in the RHIC experiments come dominantly from heavy meson decay. The ratio of their $p_T$ spectra in pp and AA collisions ($R_{AA}(p_T)$) reveals the energy loss of heavy quarks in the environment created by AA collisions. Using a fixed coupling constant and the Debye mass ($m_D\approx gT$) as infrared regulator perturbative QCD (pQCD) calculations are not able to reproduce the data, neither the energy loss nor the azimuthal $(v_2)$ distribution. Employing a running coupling constant and replacing the Debye mass by a more realistic hard thermal loop (HTL) calculation we find a substantial increase of the collisional energy loss which brings the $v_2(p_T)$ distribution as well as $R_{AA}(p_T)$ to values close to the experimental ones without excluding a contribution from radiative energy loss.