Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements ...from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (
p
T
), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high
p
T
. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements ...of π^{0} trigger particles at transverse momenta p{T}{t}=4-12 GeV/c and associated charged hadrons (p{T}{a}=0.5-7 GeV/c) vs relative azimuthal angle Δϕ in Au+Au and p+p collisions at sqrts{NN}=200 GeV. The Au+Au distribution at low p{T}{a}, whose shape has been interpreted as a medium effect, is modified for p{T}{t}<7 GeV/c. At higher p{T}{t}, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p{T}{a}, which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au+Au relative to p+p (I{AA}) is suppressed at high p{T} (I{AA}≈0.35-0.5), but less than for inclusive suppression (R{AA}≈0.2).
J.Phys.G34:S969-974,2007 Measurements of inclusive spectra of hadrons at large transverse momentum
over a broad range of energy in different collision systems have been performed
with the PHENIX ...experiment at RHIC. The data allow to study the energy and
system size dependence of the suppression observed in RAA of high-pT hadrons at
sqrt(s_NN)= 200 GeV. Due to the large energy range from sqrt(s_NN)= 22 GeV to
200 GeV, the results can be compared to results from CERN SPS at a similar
energy. The large Au+Au dataset from the 2004 run of RHIC also allows to
constrain theoretical models that describe the hot and dense matter produced in
such collisions. Investigation of particle ratios such as eta/pi0 helps
understanding the mechanisms of energy loss.
The PHENIX experiment has measured direct photons at $\sqrt{s_{NN}}$ = 200
GeV in $p+p$, $d$+Au and Au+Au collisions. For $p_{T}$ $<$ 4 GeV/$c$, the
internal conversion into $e^{+}e^{-}$ pairs has ...been used to measure the direct
photons in Au+Au.
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