Determining the spectrum of photons emitted by the quark-gluon plasma non-perturbatively remains an open computational challenge. In this letter we calculate two moments of that spectrum at a temperature T≈254MeV, employing lattice QCD with two flavors of O(a)-improved Wilson fermions, without facing an inverse problem. Our central value for the difference of these two moments, which is sensitive to photon energies ω≳πT, is lower than, but compatible with that obtained by integrating the leading-order weak-coupling photon spectrum. This study informs the direct photon puzzle in heavy-ion collision phenomenology, where it has proved difficult to simultaneously explain the yield and azimuthal anisotropy of photons not originating from final-state hadronic decays.
@article{arxiv.2505.10295,
title = {Probing how bright the quark-gluon plasma glows in lattice QCD},
author = {Ardit Krasniqi and Marco Cè and Tim Harris and Renwick J. Hudspith and Harvey B. Meyer},
journal= {arXiv preprint arXiv:2505.10295},
year = {2025}
}