Abstract
We estimate the production rate of photons by the quark-gluon plasma in lattice QCD. We propose a new correlation function which provides better control over the systematic uncertainty in estimating the photon production rate at photon momenta in the range πT/2 to 2πT. The relevant Euclidean vector current correlation functions are computed with Nf = 2 Wilson clover fermions in the chirally-symmetric phase. In order to estimate the photon rate, an ill-posed problem for the vector-channel spectral function must be regularized. We use both a direct model for the spectral function and a modelindependent estimate from the Backus-Gilbert method to give an estimate for the photon rate.
Highlights
Lattice QCD has had a tremendous impact in computing the equilibrium properties of strongly interacting matter at non-zero temperature
We present preliminary results of the photon rate using a continuum-extrapolated correlator computed with Nf = 2 flavours of O(a)-improved Wilson fermions
Pioneering numerical calculations have been performed in pure gauge theory [11], which utilized advanced perturbative results on the UV behaviour of the Euclidean correlator Gμ μ(τ, k), closely-related to the dilepton production rate, to constrain the photon rate
Summary
Lattice QCD has had a tremendous impact in computing the equilibrium properties of strongly interacting matter at non-zero temperature. The dynamical parameters of thermal systems, like transport coefficients and production rates of weakly-coupled external currents, are needed to interpret, for example, the equilibration of the thermal medium formed after a heavy-ion collision [1] or the abundance of particles in the early universe [2]. They are interesting in their own right to characterize the medium. The spectral representation of the Euclidean correlation function of the electromagnetic current, Vμem(x) = fQfψf (x)γμψ f (x) where {γμ, γν} = 2ημν = 2 diag(+, −, −, −), reads.
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