Transverse mass scaling of dilepton radiation off a quark-gluon plasma

Abstract

The spectrum of dileptons produced by the quark-gluon plasma in an ultrarelativistic nucleus-nucleus collision depends only, to a good approximation, on the transverse mass M_t of the dilepton. This scaling is exact as long as transverse flow is negligible, and the system is in local thermal equilibrium. We implement a state-of-the-art modelization of kinetic and chemical equilibration in the early stages of the evolution to study the modifications of the spectrum. Violations of M_t scaling resulting from these effects are evaluated as a function of the shear viscosity to entropy ratio (eta/s) that controls the equilibration time. We determine the dependence of the spectrum on system size, centrality, rapidity, and collision energy. We show that the quark-gluon plasma produces more dileptons than the Drell-Yan process up to invariant masses of order M = 4 GeV. Due to different kinematics, for a given M_t , the dependence of the dilepton yield on M is opposite for the two processes, so that experiment alone can in principle determine which process dominates.

9 pages, 3 figures

References in corpus (7)

• Relativistic hydrodynamics for heavy-ion collisions
• Pre-equilibrium dilepton production from an anisotropic quark-gluon plasma
• Evidence for the production of thermal muon pairs with masses above 1 GeV/c^2 in 158A GeV Indium-Indium Collisions
• NA60 results on thermal dimuons
• Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
• Intermediate mass dileptons as pre-equilibrium probes in heavy ion collisions
• The emission of electromagnetic radiation from the early stages of relativistic heavy-ion collisions

Cited by in corpus (4)

• The Present and Future of QCD
• Dilepton polarization as a signature of plasma anisotropy
• Thermal dilepton production within conformal viscous Gubser flow
• Dileptons at Colliders as Probes of the Quark-Gluon Plasma