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arXiv · 2505.10295

Probing how bright the quark-gluon plasma glows in lattice QCD

Ardit Krasniqi·Marco Cè·Tim Harris·Renwick J. Hudspith·Harvey B. Meyer
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Abstract

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 $T\approx 254\,$MeV, employing lattice QCD with two flavors of $\mathrm{O}(a)$-improved Wilson fermions, without facing an inverse problem. Our central value for the difference of these two moments, which is sensitive to photon energies $\omega\gtrsim \pi T$, is lower than, but compatible with that obtained by integrating the leading-order weak-coupling photon spectrum. This study informs the $\textit{direct photon puzzle}$ 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.

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Ardit Krasniqi, Marco Cè, Tim Harris, Renwick J. Hudspith, Harvey B. Meyer. 2025-05-15. Probing how bright the quark-gluon plasma glows in lattice QCD. https://arxiv.org/abs/2505.10295

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