The invariant differential cross section for inclusive electron production in p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider ...over the transverse momentum range 0.4 <= p_T <= 5.0 GeV/c at midrapidity (eta <= 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_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 as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.
Inclusive transverse momentum spectra of eta mesons have been measured within p_T = 2-10 GeV/c at mid-rapidity by the PHENIX experiment in Au+Au collisions at sqrt(s_NN) = 200 GeV. In central Au+Au ...the eta yields are significantly suppressed compared to peripheral Au+Au, d+Au and p+p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality and p_T dependence of the suppression is common, within errors, for eta and pi^0. The ratio of eta to pi^0 spectra at high p_T amounts to 0.40 < R_eta/pi^0 < 0.48 for the three systems in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e^+e^- collisions.
We report on leptonic observables by the PHENIX experiment from data taken during Run II at the Relativistic Heavy Ion Collider (RHIC). We show first results on φ →
K
+
K
−,
e
+
e
−, low and ...intermediate mass dielectron continuum, single electrons from charm, and
J/ψ yields in proton-proton and Au
Au collisions at
S
N
N
=
200
GeV.
Charged particle event-by-event fluctuations have long been considered as a possible signature of quark gluon plasma formation in ultra-relativistic heavy-ion collisions 1. That the interest in ...fluctuations remains high in the era of RHIC is evidenced by the large number of recent theoretical 2–4, as well as experimental 5–7, studies published since the previous Quark Matter conference. Here, new results from the PHENIX experiment on event-by-event fluctuations in net charge and <
p
T
> in Au+Au interactions at
S
N
N
=
200
will be presented.
The PHENIX experiment measured J/\(\psi\) production in pp, d + Au and Au + Au reactions at \(\sqrt{s_{NN}}\) = 200 GeV over a wide range of rapidity and transverse momentum. The nuclear modification ...factor obtained by comparing the d + Au and pp cross sections as a function of rapidity, is consistent with shadowing of the gluon distribution functions. J/\(\psi\) production in Au + Au collisions was compared to the production in pp collisions and it was found to be inconsistent with models that predict strong enhancement relative to binary collision scaling.
Transverse momentum $\P_{T}$ spectra measured by the PHENIX experiment at RHIC in Au + Au, d + Au and pp collisions at $\sqrt {^S{NN}} = 200 GeV$ and in Au + Au collisions at $\sqrt {^S{NN}} = 62.4 ...GeV$ are presented. A suppression of the yield of high $\P_{T}$ hadrons in central Au + Au collisions by a factor 4-5 at $\P_{T}>5$ is found relative to the pp reference scaled by the nuclear overlap function $(\T_{AB})$ . In contrast, direct photons are not suppressed in central Au + Au collisions and no suppression of high $\P_{T}$ particles can be seen in d + Au collisions. This leads to the conclusion that the dense medium formed in central Au + Au collisions is responsible for the suppression.
Heavy flavor production in PHENIX Drapier, O
European Physical Journal C: Particles and Fields,
08/2005, Volume:
43, Issue:
1-4
Journal Article, Conference Proceeding
Peer reviewed
Open access
The PHENIX experiment at RHIC measured single electron spectra in p + p, d + Au and Au + Au collisions at \(\sqrt{s_{NN}} = 200\) GeV, and in Au + Au collisions at \(\sqrt{s_{NN}} = 62.4\) GeV. In ...these spectra, electrons from semi-leptonic decays of charmed particles are the dominant contribution after subtraction of all 'photonic' sources (photon conversions, Dalitz decays, decays of light vector mesons). The p + p open charm production cross-section is found to be in good agreement with pQCD NLO calculations. The shape of the distributions obtained for p + p interactions is compared with those observed for nucleus-nucleus collisions. From p + p to d + Au and Au + Au interactions, open charm production is found to scale with the number of binary collisions \(N_{\rm coll}\). Au + Au data at \(\sqrt{s_{NN}} = 62.4\) GeV is compatible with the ISR p + p results scaled by \(N_{\rm coll}\). The elliptic flow parameter v2 of heavy flavor electrons has also been measured, and is found to be non-zero in the intermediate pT range.
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