ϕmeson production ind+Aucollisions atsNN

Abstract

The PHENIX collaboration has measured φ meson production in d+Au collisions at √ s N N = 200 GeV using the dimuon and dielectron decay channels. The φ meson is measured in the forward (backward) d-going (Au-going) direction, 1.2 < y < 2.2 (−2.2 < y < −1.2) in the transversemomentum (pT ) range from 1-7 GeV/c, and at midrapidity |y| < 0.35 in the pT range below 7 GeV/c. The φ meson invariant yields and nuclear-modification factors as a function of pT , rapidity, and centrality are reported. An enhancement of φ meson production is observed in the Au-going direction, while suppression is seen in the d-going direction, and no modification is observed at midrapidity relative to the yield in p+p collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor indicating similar cold-nuclear-matter effects.

Virtual photon polarization in ultrarelativistic heavy-ion collisions

“…The dilepton angular distribution in In-In collisions has been measured by the NA60 experiment [12] at the CERN-SPS in the primary kinematical range 0.4 < M l + l − < 0.9 GeV, in which production of dileptons by hadronic sources such as π + π − annihilation dominates Drell-Yan dileptons; the results are consistent with λ = µ = ν = 0. On the other hand, in ultrarelativistic heavy-ion collisions we expect the momentum-space anisotropy of the QGP to be detected most readily in dilepton production in the range 1 GeV < q T < 3 GeV and M l + l − < ∼ 0.3 GeV where the excess of direct photons is seen experimentally [1]. In this paper, we present a general framework for analyzing the angular distribution of dileptons emitted from a QGP, which can be used to extract quark and gluon momentum anisotropies in the collision.…”

“…Direct photons, both real and virtual, are an important probe of the dynamics of ultrarelativistic heavy-ion collisions. An average temperature of the quark-gluon plasma (QGP) formed in high-energy collisions has been extracted from the transverse momentum spectrum of direct photons in the range q T ∼ 1-3 GeV [1][2][3]. Theoretically, measurements of the photon polarization through the angular distribution of dileptons (l + l − ) have been proposed to provide information on the early stages of collisions, before the onset of thermalization [4][5][6].…”

“…As an illustration, we apply the formalism to virtual photon emission through the leading-order Drell-Yan process in a plasma with anisotropic distributions of the Romatschke-Strickland form [13]. 1…”

Photon and dilepton observables: An experimental overview

“…Newly published heavy flavor cross-section measurements in √ s NN = 200 GeV p+p and d+Au collisions were shown by the PHENIX experiment. [14] The cross-sections are obtained by fitting the dielectron…”

Modeling of two-particle femtoscopic correlations at top RHIC energy

“…the Ultra Relativistic Quantum Molecular Dynamics Model (UrQMD) [2,3,4,5] was used to simulate the ion collisions. The calculated femtoscopic radii for Au+Au collisions were compared to the STAR [6] and PHENIX experimental data [7].…”