Thermal photon, dilepton production, and electric charge transport in a baryon rich strongly coupled QGP from holography

Abstract

We obtain the thermal photon and dilepton production rates in a strongly coupled quark-gluon plasma (QGP) at both zero and nonzero baryon chemical potentials using a bottom-up Einstein-Maxwell-dilaton holographic model that is in good quantitative agreement with the thermodynamics of (2+1)-flavor lattice QCD around the crossover transition for baryon chemical potentials up to 400 MeV, which may be reached in the beam energy scan at RHIC. We find that increasing the temperature T and the baryon chemical potential μB enhances the peak present in both spectra. We also obtain the electric charge susceptibility, the dc and ac electric conductivities, and the electric charge diffusion as functions of T and μB. We find that electric diffusive transport is suppressed as one increases μB. At zero baryon density, we compare our results for the dc electric conductivity and the electric charge diffusion with the latest lattice data available for these observables and find reasonable agreement around the crossover transition. Therefore, our holographic results may be used to constraint the magnitude of the thermal photon and dilepton production rates in a strongly coupled QGP, which we found to be at least 1 order of magnitude below perturbative estimates.