Toward an understanding of the single electron data measured at the BNL Relativistic Heavy Ion Collider (RHIC)

Abstract

High transverse momentum (${p}_{T}$) single nonphotonic electrons which have been measured in the RHIC experiments come dominantly from heavy meson decay. The ratio of their ${p}_{T}$ spectra in $\mathit{pp}$ and $\mathit{AA}$ collisions [${R}_{\mathit{AA}}({p}_{T})$] reveals the energy loss of heavy quarks in the environment created by $\mathit{AA}$ collisions. Using a fixed coupling constant and the Debye mass (${m}_{D}\ensuremath{\approx}\mathit{gT}$) as the 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 in the collisional energy loss, which brings the ${v}_{2}({p}_{T})$ distribution as well as ${R}_{\mathit{AA}}({p}_{T})$ to values close to the experimental ones without excluding a contribution from radiative energy loss.