PHENIX measurements of low momentum direct photon radiation

Abstract

The versatility of RHIC allowed the PHENIX collaboration to measure low momentum direct photons from small systems, such as p+p, p+A, d+Au at $\sqrt{s_{NN}}=$200 GeV as well as from large A+A systems, such as Au+Au and Cu+Cu at 200 GeV and Au+Au at 62.4 GeV and 39 GeV. In these measurements PHENIX has discovered a large excess over the scaled p+p yield of direct photons in A+A collisions, and a non-zero excess over the scaled p+p yield in central p+A collisions. Another PHENIX discovery is that at low-$p_T$ the integrated yield of direct photons, $d{N}_{\gamma }/dy$, from large systems follows a universal scaling as a function of the charged-particle multiplicity, $(d{N}_{ch}/d\eta {)}^{\alpha }$, with $\alpha =1.25$. The observed scaling properties of direct photons from these systems show that the photon production yield increases faster than the charged-particle multiplicity.

arXiv commentProceedings for the XXVIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018)

References in corpus (12)

• Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Enhanced production of direct photons in Au+Au collisions at sqrt(s_NN)=200 GeV and implications for the initial temperature
• The production of photons in relativistic heavy-ion collisions
• Direct photon production in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$ = 2.76 TeV
• Measurement of Direct Photons in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Azimuthally anisotropic emission of low-momentum direct photons in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Transverse energy production and charged-particle multiplicity at midrapidity in various systems from $\sqrt{s_{NN}}=7.7$ to 200 GeV
• Pseudo-Critical Enhancement of Thermal Photons in Relativistic Heavy-Ion Collisions
• Direct photon production in d+Au collisions at sqrt(s_NN)=200 GeV
• Beam-energy and centrality dependence of direct-photon emission from ultra-relativistic heavy-ion collisions
• Direct Photon Elliptic Flow at BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)
• Low-momentum direct photon measurement in Cu$+$Cu collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

Cited by in corpus (7)

• Photon production and elliptic flow from momentum-anisotropic quark-gluon plasma
• Prompt photon production in high-energy $pA$ collisions at forward rapidity
• Scaling properties of direct photon yields in heavy ion collisions
• Photon spectra and anisotropic flow in heavy ion collisions at the top RHIC energy within the integrated hydrokinetic model with photon hadronization emission
• Geometrical scaling of prompt photons in heavy ion collisions
• Geometrical Scaling of Direct Photons in Relativistic Heavy Ion and d+Au Collisions
• Shining a Light on the QGP - Electroweak Probes Experimental Summary