Measurements of directed, elliptic, and triangular flow in Cu++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

International audienceMeasurements of anisotropic flow Fourier coefficients (vn) for inclusive charged particles and identified hadrons π±, K±, p, and p¯ produced at midrapidity in Cu+Au collisions at sNN=200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes Ψn, for n=1, 2, and 3 are studied as a function of transverse momentum pT over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu+Au results with those in Cu+Cu and Au+Au collisions at the same sNN and find that the v2 and v3, as a function of transverse momentum, follow a common scaling with 1/(ɛnNpart1/3)

Forward J/ψJ/\psi production in U++U collisions at sNN\sqrt{s_{NN}}=193 GeV

International audienceThe invariant yields, dN/dy, for J/ψ production at forward rapidity (1.2<|y|<2.2) in U+U collisions at sNN=193GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor RAA are presented and compared with those from Au+Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U+U and Au+Au collisions within the same centrality class is presented, and used to investigate the role of cc¯ coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, Ncoll, and these were found to give significantly different Ncoll values. Results using Ncoll values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the J/ψ suppression, relative to binary collision scaling, is similar in U+U and Au+Au for peripheral and midcentral collisions, but that J/ψ show less suppression for the most central U+U collisions. The results are consistent with a picture in which, for central collisions, increase in the J/ψ yield due to cc¯ coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between cc¯ coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine Ncoll

ϕ\phi meson production in the forward/backward rapidity region in Cu++Au collisions at sNN=200\sqrt{s_{NN}}=200 GeV

International audienceThe PHENIX experiment at the Relativistic Heavy Ion Collider has measured ϕ meson production and its nuclear modification in asymmetric Cu+Au heavy-ion collisions at sNN=200 GeV at both forward Cu-going direction (1.2<y<2.2) and backward Au-going direction (−2.2<y<−1.2) rapidities. The measurements are performed via the dimuon decay channel and reported as a function of the number of participating nucleons, rapidity, and transverse momentum. In the most central events, 0%–20% centrality, the ϕ meson yield integrated over 1<pT<5 GeV/c prefers a smaller value, which means a larger nuclear modification, in the Cu-going direction compared to the Au-going direction. Additionally, the nuclear-modification factor in Cu+Au collisions averaged over all centrality is measured to be similar to the previous PHENIX result in d+Au collisions for these rapidities

Shape, transverse size, and charged-hadron multiplicity of jets in pp collisions at sqrts=7;TeV sqrt {s} = 7;TeV

Measurements of jet characteristics from inclusive jet production in proton-proton collisions at a centre-of-mass energy of 7 TeV are presented. The data sample was collected with the CMS detector at the LHC during 2010 and corresponds to an integrated luminosity of 36 inverse picobarns. The mean charged hadron multiplicity, the differential and integral jet shape distributions, and two independent moments of the shape distributions are measured as functions of the jet transverse momentum for jets reconstructed with the anti-kT algorithm. The measured observables are corrected to the particle level and compared with predictions from various QCD Monte Carlo generators.Comment: Replaced with published version. Added journal reference and DOI. Supplementary data tables availabl