Emission source functions are extracted from correlation functions constructed from charged pions produced at midrapidity in Au+Au collisions at {radical}(s{sub NN})=200 GeV. The source parameters ...extracted from these functions at low k{sub T} give first indications of a long tail for the pion emission source. The source extension cannot be explained solely by simple kinematic considerations. The possible role of a halo of secondary pions from resonance emissions is explored.
The dependence of transverse momentum spectra of neutral pions and {eta} mesons with p{sub T}<16 GeV/c and p{sub T}<12 GeV/c, respectively, on the centrality of the collision has been measured at ...midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) in d+Au collisions at {radical}(s{sub NN})=200 GeV. The measured yields are compared to those in p+p collisions at the same {radical}(s{sub NN}) scaled by the number of underlying nucleon-nucleon collisions in d+Au. At all centralities, the yield ratios show no suppression, in contrast to the strong suppression seen for central Au+Au collisions at RHIC. Only a weak p{sub T} and centrality dependence can be observed.
The azimuthal distribution of identified {pi}{sup 0} and inclusive photons has been measured in {radical}(s{sub NN})=200 GeV Au+Au collisions with the PHENIX experiment at the Relativistic Heavy-Ion ...Collider (RHIC). The second-harmonic parameter (v{sub 2}) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon v{sub 2} is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured p{sub T} range 1-6 GeV/c. An attempt is made to extract v{sub 2} of direct photons.
The PHENIX experiment has measured midrapidity (vertical bar {eta} vertical bar <0.35) transverse momentum spectra (0.4<p{sub T}<5.0 GeV/c) of electrons as a function of centrality in Au+Au ...collisions at {radical}(s{sub NN})=200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of {pi}{sup 0} and {eta} mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high p{sub T} is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.
The invariant differential cross section for inclusive electron production in p+p collisions at {radical}(s)=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion ...Collider over the transverse momentum range 0.4{<=}p{sub T}{<=}5.0 GeV/c in the central rapidity region (vertical bar {eta} vertical bar {<=}0.35). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e., charm quarks or, at high p{sub T}, bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy-flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined to be {sigma}{sub cc}=0.92{+-}0.15(stat){+-}0.54(syst) mb.
Cross sections for midrapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for transverse momenta of 3<p{sub T}<16 GeV/c. Next-to-leading ...order perturbative QCD (pQCD) describes the data well for p{sub T}>5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for p{sub T}>7 GeV/c.
J/{psi} production in d+Au and p+p collisions at {radical}(s{sub NN})=200 GeV has been measured by the PHENIX experiment at rapidities -2.2<y<+2.4. The cross sections and nuclear dependence of ...J/{psi} production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p+A results and to theoretical models. The observed nuclear dependence in d+Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parametrizations that fit deep-inelastic scattering and Drell-Yan data at lower energies.
The sPHENIX Time Projection Chamber Outer Tracker (TPOT) is a Micromegas based detector. It is a part of the sPHENIX experiment that aims to facilitate the calibration of the Time Projection Chamber, ...in particular the correction of the time-averaged and beam-induced distortions of the electron drift. This paper describes the detector mission, setup, construction, installation, commissioning and performance during the first year of sPHENIX data taking.
The first measurement of direct photons in Au+Au collisions at {radical}(s{sub NN})=200 GeV is presented. The direct photon signal is extracted as a function of the Au+Au collision centrality and ...compared to next-to-leading order perturbative quantum chromodynamics calculations. The direct photon yield is shown to scale with the number of nucleon-nucleon collisions for all centralities.
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