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 sNN=200GeV as well as from large A+A systems, such as ...Au+Au and Cu+Cu at 200GeV and Au+Au at 62.4GeV and 39GeV. 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-pT the integrated yield of direct photons, dNγ/dy, from large systems follows a universal scaling as a function of the charged-particle multiplicity, (dNch/dη)α, with α = 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.
At the Quark Matter 2018 conference, the PHENIX Collaboration gave 10 parallel talks and 19 posters on a wide variety of topics in small and large systems. In these proceedings we discuss a few key ...results shown at the conference.
Using the extraordinary versatility of RHIC in selecting different colliding species, the PHENIX experiment has collected data in p+Al, p+Au, d+Au, and 3He+Au collisions at 200 GeV center-of-mass ...energy and conducted a comprehensive set of anisotropic flow measurements. These geometry-controlled experiments provide a unique testing ground for theoretical models that produce azimuthal particle correlations based on initial- and/or final-state effects.
A complete set of triangular anisotropies of inclusive charged particles and final results on identified pion and proton v2(pT) are shown. The mass-ordered splitting in v2(pT) provides information about the role of early-stage collective flow and late-stage hadronic rescattering. Detailed model comparisons with all observables are discussed.
Quarkonium suppression in nucleus-nucleus collisions is a powerful tool to probe the density and temperature of the medium created in heavy ion collisions. Forward rapidity measurements in p(d)+Au ...collisions are essential to understand how quarkonium states are affected by initial state effects, formation time, and local particle multiplicity. Earlier measurements in Au+Au collisions showed a stronger suppression of forward J/ψ compared to mid-rapidity results, indicating the possibility of a smaller contribution of regenerated quarkonium states at forward rapidity. These proceedings report on the latest quarkonium studies performed by the PHENIX collaboration in the rapidity range 1.2<|y|<2.2.
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