Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

International audienceWe present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1<|η|<3 in Au + Au collisions at sNN=200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v2{2},v2{4},v2{6}, and v2{8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v2 distribution from v2{2} and v2{4}. In a complementary analysis, we also use a folding procedure to study the distributions of v2 and v3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed

Charm- and Bottom-Quark Production in Au++Au Collisions at sNN\sqrt{s_{_{NN}}} = 200 GeV

The invariant yield of electrons from open-heavy-flavor decays for $1<p_T<8$ GeV/$c$ at midrapidity $|y|<0.35$ in Au$+$Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. A displaced-vertex analysis with the PHENIX silicon-vertex detector enables extraction of the fraction of charm and bottom hadron decays and unfolding of the invariant yield of parent charm and bottom hadrons. The nuclear-modification factors $R_{AA}$ for electrons from charm and bottom hadron decays and heavy-flavor hadrons show both a centrality and a quark-mass dependence, indicating suppression in the quark-gluon plasma produced in these collisions that is medium sized and quark-mass dependent

Measurement of J/ψJ/\psi at forward and backward rapidity in p+pp+p, p+Ap+Al, p+Ap+Au, and 3^3He++Au collisions at sNN=200 GeV\sqrt{s_{_{NN}}}=200~{\rm GeV}

International audienceCharmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of charmonium in small systems have become increasingly relevant. We present the results of J/ψ measurements at forward and backward rapidity in various small collision systems, p+p, p+Al, p+Au, and He3+Au, at sNN=200 GeV. The results are presented in the form of the observable RAB, the nuclear modification factor, a measure of the ratio of the J/ψ invariant yield compared to the scaled yield in p+p collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on J/ψ production with different projectile sizes p and He3, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for p+Au and He3+Au. However, for 0%–20% central collisions at backward rapidity, the modification factor for He3+Au is found to be smaller than that for p+Au, with a mean fit to the ratio of 0.89±0.03(stat)±0.08(syst), possibly indicating final state effects due to the larger projectile size

Measurement of ϕ\phi-meson production at forward rapidity in p+pp+p collisions at s=510 GeV\sqrt{s}=510\text{ }\text{ }\mathrm{GeV} and its energy dependence from s=200 GeV\sqrt{s}=200\text{ }\text{ }\mathrm{GeV} to 7 TeV

International audienceThe PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of ϕ(1020)-meson production at forward rapidity in p+p collisions at s=510  GeV via the dimuon decay channel. The partial cross section in the rapidity and pT ranges 1.2<|y|<2.2 and 2<pT<7  GeV/c is σϕ=[2.28±0.09(stat)±0.14(syst)±0.27(norm)]×10-2  mb. The energy dependence of σϕ (1.2<|y|<2.2,2<pT<5  GeV/c) is studied using the PHENIX measurements at s=200 and 510 GeV and the Large Hadron Collider measurements at s=2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc)

Charm- and Bottom-Quark Production in Au++Au Collisions at sNN\sqrt{s_{_{NN}}} = 200 GeV

The invariant yield of electrons from open-heavy-flavor decays for $1<p_T<8$ GeV/$c$ at midrapidity $|y|<0.35$ in Au$+$Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. A displaced-vertex analysis with the PHENIX silicon-vertex detector enables extraction of the fraction of charm and bottom hadron decays and unfolding of the invariant yield of parent charm and bottom hadrons. The nuclear-modification factors $R_{AA}$ for electrons from charm and bottom hadron decays and heavy-flavor hadrons show both a centrality and a quark-mass dependence, indicating suppression in the quark-gluon plasma produced in these collisions that is medium sized and quark-mass dependent

Nonprompt direct-photon production in Au++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

The measurement of the direct-photon spectrum from Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV is presented by the PHENIX collaboration using the external-photon-conversion technique for 0%--93% central collisions in a transverse-momentum ($p_T$) range of 0.8--10 GeV/$c$. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for $p_T<6$ GeV/$c$. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as $N_{\rm coll}$-scaled direct photons from $p$ $+$ $p$ collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for $0.8<p_T<6.0$ GeV/$c$ and suggest that the spectrum has an increasing inverse slope from ${\approx}0.2$ to 0.4 GeV/$c$ with increasing $p_T$, which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the $p_T$-integrated nonprompt direct-photon yields also follow a power-law scaling behavior as a function of collision-system size. The exponent, $\alpha$, for the nonprompt component is found to be consistent with 1.1 with no apparent $p_T$ dependence

Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at s=510\sqrt{s}=510 GeV in p⃗+p⃗\vec{p}+\vec{p} Collisions

We present the measurement of the cross section and double-helicity asymmetry $A_{LL}$ of direct-photon production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV. The measurement has been performed at midrapidity ($|\eta|<0.25$) with the PHENIX detector at the Relativistic Heavy Ion Collider. Direct photons are dominantly produced by the quark-gluon scattering at relativistic energies. Direct photons are produced from the initial partonic hard scattering and do not interact via the strong force. Therefore, this measurement provides a clean and direct access to the gluons in the polarized proton in the gluon-momentum-fraction range $0.02<x<0.08$