In-medium spectral functions and dilepton rates with the Functional Renormalization Group

TL;DR

This paper uses the Functional Renormalization Group to compute in-medium spectral functions and dilepton rates in a QCD-inspired model, exploring chiral symmetry restoration and potential experimental signatures in the phase diagram.

Contribution

It introduces an analytic continuation method within the FRG framework to calculate real-time spectral functions at finite temperature and density in an effective QCD model.

Findings

The $ ho$ and $a_1$ spectral functions become degenerate at high T or chemical potential.

Preliminary dilepton rates show potential signatures of chiral crossover and the critical endpoint.

The method enables real-time spectral calculations in a non-perturbative QCD model.

Abstract

We present recent results on in-medium spectral functions of vector and axial-vector mesons, the electromagnetic (EM) spectral function and dilepton rates using the Functional Renormalization Group (FRG) approach. Our method is based on an analytic continuation procedure that allows us to calculate real-time quantities like spectral functions at finite temperature and chemical potential. As an effective low-energy model for Quantum Chromodynamics (QCD) we use an extended linear-sigma model including quarks where (axial-)vector mesons as well as the photon are introduced as gauge bosons. In particular, it is shown how the $\rho$ and the $a_1$ spectral function become degenerate at high temperatures or chemical potentials due to the restoration of chiral symmetry. Preliminary results for the EM spectral function and the dilepton production rate are discussed with a focus on the possibility to identify signatures of the chiral crossover and the critical endpoint (CEP) in the QCD phase diagram.