Hadronic production of thermal photons

Abstract

We study the thermal emission of photons from hot and dense strongly interacting hadronic matter at temperatures close to the expected phase transition to the Quark-Gluon Plasma (QGP). Earlier calculations of photon radiation from ensembles of interacting mesons are re-examined with additional constraints, including new production channels as well as an assessment of hadronic form factor effects. Whereas strangeness-induced photon yields turn out to be moderate, the hitherto not considered t-channel exchange of ω-mesons is found to contribute appreciably for photon energies above ∼ 1.5 GeV. The role of baryonic effects is assessed using existing many-body calculations of lepton pair production. We argue that our combined results constitute a rather realistic emission rate, appropriate for applications in relativistic heavy-ion collisions. Supplemented with recent evaluations of QGP emission, and an estimate for primordial (hard) production, we compute photon spectra at SPS, RHIC and LHC energies.

Electromagnetic Probes in PHENIX

“…7. Partial contributions are calculated in [14,20] and the solid curve is the sum of all subprocesses; it describes the data very well. Remarkably, this calculation uses an expanding fireball with τ 0 = 0.33fm/c and T i = 370MeV, double the formation time and only 2/3 of the temperature conjectured in [21] and applied on Fig.…”

“…6 that the overall yields of high-p T photons (integrated over azimuth) scale Predictions for direct photon spectra combining pQCD initial, jet-plasma interactions [20] as well as thermal radiation [14], compared to preliminary PHENIX data. The lines labeled "Th-Th" and "HG" correspond to the usual thermal radiation from QGP and hadron gas, respectively.…”

Photon emission from dense quark matter

“…Ref. [13] for a recent analysis in hot hadronic matter). We will comment on the effects of kaons and other strangeness-bearing mesons in the summary.…”

Electromagnetic signals from Au + Au collisions at RHIC energy, sNN=200 GeV and Pb + Pb collisions at LHC energy, Nayak1, Sinha2 2013Physics Letters B5020View full textAdd to dashboardCite

“…[38][39][40][41]. The contributions from the reactions involving strange mesons like πK * → Kγ, πK → K * γ, ρK → Kγ and KK * → Kγ, have been pointed out in [42] Contributions from other decays, such as K * (892) → K γ, φ → η γ, b 1 (1235) → π γ, a 2 (1320) → π γ and K 1 (1270) → π γ have been found to be small [43] for p T > 1 GeV. We consider all the processes for our calculation.…”

“…All the isospin combinations for the above reactions and decays have properly been taken into account. The effects of hadronic form factors(dipole) [42] have been incorporated.…”