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

TL;DR

This paper uses holography to calculate thermal photon and dilepton production rates, electric charge transport properties, and their dependence on temperature and baryon chemical potential in a strongly coupled quark-gluon plasma, aligning well with lattice QCD data.

Contribution

It introduces a holographic model that accurately reproduces thermodynamics and transport coefficients of a baryon-rich QGP, providing new insights into electromagnetic emissions and charge diffusion at finite baryon density.

Findings

Photon and dilepton spectra peak increase with T and μ_B.

Electric charge diffusion decreases as μ_B increases.

Holographic results agree with lattice data at zero baryon density.

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 potential using a bottom-up Einstein-Maxwell-Dilaton (EMD) 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 (BES) at RHIC. We find that increasing the temperature $T$ and the baryon chemical potential $\mu_B$ 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 $\mu_B$. We find that electric diffusive transport is suppressed as one increases $\mu_B$. 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 one order of magnitude below perturbative estimates.