Estimation of the photon production rate using imaginary momentum correlators

TL;DR

This paper introduces a novel method to estimate the thermal photon production rate by calculating the Euclidean correlator at imaginary spatial momentum, addressing the challenge of spectral function extraction from Euclidean data.

Contribution

It presents the first implementation of directly computing the analytic continuation of the retarded correlator at fixed photon virtuality using imaginary momentum techniques.

Findings

First results on photon production rate estimation at 250 MeV.

Demonstrates feasibility of using imaginary momentum correlators for spectral function analysis.

Provides a new approach to access electromagnetic spectral functions in lattice QCD.

Abstract

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O(a)-improved Wilson fermions at a temperature of 250 MeV.