Rate of photon production in the quark-gluon plasma from lattice QCD

Cè, Marco; Harris, Tim; Meyer, Harvey B.; Steinberg, Aman; Toniato, Arianna

doi:10.1103/physrevd.102.091501

Cited by 23 publications

(41 citation statements)

References 35 publications

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“…In general, the non-negativity of 𝜎 𝑇 implies that the area can be no smaller for the 𝑛 = 2 than for the 𝑛 = 1 correlator. The calculation is performed on a 24 × 96 3 lattice QCD ensemble with two dynamical flavours of light quarks and 𝑇 254 MeV, the X7 ensemble described in [5]. The displayed data is based on 1331 configurations, with 64 point sources used per configuration.…”

Section: Probing the Structure Functions With Euclidean Correlation Functionsmentioning

confidence: 99%

Deep inelastic scattering on the quark-gluon plasma

Cè

Harris

Meyer

et al. 2021

J. High Energ. Phys.

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We provide an interpretation of the structure functions of a thermal medium such as the quark-gluon plasma in terms of the scattering of an incoming electron on the medium via the exchange of a spacelike photon. We then focus on the deep-inelastic scattering (DIS) regime, and formulate the corresponding moment sum rules obeyed by the structure functions. Accordingly, these moments are given by the thermal expectation value of twist-two operators, which is computable from first principles in lattice QCD for the first few moments. We also show how lattice QCD calculations can be used to probe how large the photon virtuality needs to be in order for the Bjorken scaling of structure functions to set in. Finally, we provide the parton-model interpretation of the structure functions in the Bjorken limit and test its consistency. As in DIS on the proton, the kinematic variable x is proportional to the longitudinal momentum carried by the partons, however x ranges from zero to infinity. Choosing the parton momentum parametrization to be xT u where u is the fluid four-velocity and T its temperature in the rest frame, the parton distribution function for a plasma of non-interacting quarks is proportional to x log(1 + e−x/2).

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Section: Probing the Structure Functions With Euclidean Correlation Functionsmentioning

confidence: 99%

Deep inelastic scattering on the quark-gluon plasma

Cè

Harris

Meyer

et al. 2021

J. High Energ. Phys.

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“…The aspect ratio for the finite-temperature ensembles was set to L 0 /L = 1/4, and for the vacuum ensembles to L 0 /L = 2. The thermal ensembles were recently used in a study of the photon emissivity of the quark-gluon plasma [18]. Two of them have common bare parameters with the vacuum ensembles, while two additional ensembles with lattice spacings down to a 0.033 fm allow the continuum limit of the thermal observable to be obtained with reduced uncertainty.…”

Section: Non-perturbative Test In N F = 2 Qcdmentioning

confidence: 99%

Vacuum correlators at short distances from lattice QCD

Cè

Harris

Meyer

et al. 2021

J. High Energ. Phys.

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Non-perturbatively computing the hadronic vacuum polarization at large photon virtualities and making contact with perturbation theory enables a precision determination of the electromagnetic coupling at the Z pole, which enters global electroweak fits. In order to achieve this goal ab initio using lattice QCD, one faces the challenge that, at the short distances which dominate the observable, discretization errors are hard to control. Here we address challenges of this type with the help of static screening correlators in the high-temperature phase of QCD, yet without incurring any bias. The idea is motivated by the observations that (a) the cost of high-temperature simulations is typically much lower than their vacuum counterpart, and (b) at distances x3 far below the inverse temperature 1/T, the operator-product expansion guarantees the thermal correlator of two local currents to deviate from the vacuum correlator by a relative amount that is power-suppressed in (x3T). The method is first investigated in lattice perturbation theory, where we point out the appearance of an O(a2 log(1/a)) lattice artifact in the vacuum polarization with a prefactor that we calculate. It is then applied to non-perturbative lattice QCD data with two dynamical flavors of quarks. Our lattice spacings range down to 0.049 fm for the vacuum simulations and down to 0.033 fm for the simulations performed at a temperature of 250 MeV.

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“…For temperatures above 180 MeV, the electromagnetic emission rate used are those for a weakly-coupled quark-gluon plasma [43], extrapolated to a fixed coupling of g s = 2; below 180 MeV, hadronic thermal photon emission rates are used [44][45][46]. The exact photon emission rates for temperatures in the QCD cross-over is still under investigation [47][48][49]. To approximate the transition from partonic to hadronic rates in this temperature regime, we choose a transition temperature of T = 180 MeV, as done previously in the literature [14].…”

Section: Model Descriptionmentioning

confidence: 99%

A Non-Equilibrium Approach to Photon Emission from the Late Stages of Relativistic Heavy-Ion Collisions

et al. 2021

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In this work, we assess the importance of non-equilibrium dynamics in the production of photons from the late stages of relativistic heavy-ion collisions. The pT-differential spectra and v2 of photons from the late hadronic stage are computed within a non-equilibrium hadron transport approach, and compared to the results of a local equilibrium evolution using ideal relativistic hydrodynamics. It is found that non-equilibrium dynamics enhance the late-stage photon production at low pT and decreases it at higher pT compared to the estimate from hydrodynamics. This same comparison points to a significant increase in the momentum anisotropies of these photons due to non-equilibrium dynamics. Once combined with photons produced above the particlization temperature in the hydrodynamics evolution, the differences between the two approaches appear modest in what concerns the pT differential spectra, but are clearly noticeable at low pT for the elliptic flow: non-equilibrium dynamics enhance the photon v2 below pT ≈ 1.4 GeV.

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Rate of photon production in the quark-gluon plasma from lattice QCD

Cited by 23 publications

References 35 publications

Deep inelastic scattering on the quark-gluon plasma

Deep inelastic scattering on the quark-gluon plasma

Vacuum correlators at short distances from lattice QCD

A Non-Equilibrium Approach to Photon Emission from the Late Stages of Relativistic Heavy-Ion Collisions

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