Event anisotropy is expected to have sensitivity to the early stage of ultra-relativistic heavy-ion collisions at RHIC. The possible formation of a quark gluon plasma (QGP) could affect how the ...initial anisotropy in the space coordinate is transfered into the momentum space for the initial state. The anisotropy parameter (v
2) is an amplitude of the 2nd harmonic parameter of the azimuthal distribution with respect to the reaction plane. We present here v
2 of identified and inclusive charged particles measured in the PHENIX central arm detector (∣η∣ < 0.35) with respect to the reaction plane defined at ∣η∣ = 3 ∼ 4 in 200 GeV Au + Au collisions. We find that v
2 increases from central to mid-central collisions reaching a maximum at about 50% of the geometric cross section and then decreases again for more peripheral collisions. As a function of transverse momentum in minimum-bias collisions, the v
2 parameter increases linearly with p
T up to p
T ≅ 2 GeV/c and then saturates for inclusive charged particles. the v
2 parameter of identified particles (π
+, π
−,
K
+,
K
−,
p and
p
¯
follow a hydro-dynamic behavior up to 2 GeV/c in p
T, where the lighter mass particles haver larger v
2 at a given p
T. However there is an indication that this trend is reversed at around p
T ≅ 2GeV/c, where
p and
p
¯
have larger v
2 than π and
K.
Recent results on identified hadrons from the PHENIX experiment in Au+Au collisions at mid-rapidity at
S
N
N
=
200
GeV are presented. The centrality dependence of transverse momentum distributions ...and particle ratios for identified charged hadrons are studied. The transverse flow velocity and freeze-out temperature are extracted from
p
T
spectra within the framework of a hydrodynamic collective flow model. Two-particle HBT correlations for charged pions are measured in different centrality selections for a broad range of transverse momentum of the pair. Results on elliptic flow measurements with respect to the reaction plane for identified particles are also presented.
A new single-sided silicon strip detector has been developed for the silicon vertex tracker of the PHENIX detector at the Relativistic Heavy Ion Collider in Brookhaven National Laboratory (BNL). The ...novel "stripixel" detector concept developed by the BNL Instrumentation Division was applied to the first prototype silicon sensor. The novel feature of the stripixel concept is two-dimensional (2-D) position sensitivity with single-sided processing achieved by charge sharing between two interleaved electrodes in one pixel. Signals are read out projectively by double layers of aluminum strips. The first prototype stripixel sensors with the size of 34.3 /spl times/ 64.6 mm and thickness of 250 and 400 /spl mu/m were fabricated. The detector with readout electronics was constructed to evaluate the prototype sensor performance by using an analog multiplexer chip with charge sensitive preamplifier-shaper circuits (VA2 chip of IDEAS). The sensor performance on charge sharing, detection efficiency, signal-to-noise ratio, and position resolution has been tested with a radioactive source and a GeV particle beam at KEK-PS. The stripixel detector concept, the specification of the first prototype stripixel sensor, and the test results are presented.
We present results on charged particle (
dN
ch
/
dη) and transverse energy densities (
dE
T/
dη) measured at mid-rapidity in Au
Au collisions at
S
N
N
=
200
GeV. The mean transverse energy per ...charged particle is derived. The results are presented as a function of centrality, which is defined by the number of participating nucleons (
N
p
), and compared to results obtained in Au
Au collisions at
S
N
N
=
130
GeV. A comparison with calculations from various theoretical models is performed.
The NA60 experiment at the CERN SPS studies dimuon production in proton and heavy ion collisions. Its silicon pixel vertex telescope allows tracking of muon pairs in the vertex region, complementing ...the information from the muon spectrometer, and improving the mass resolution and signal-to-noise ratio. First results from the In-In data taking are shown for the light resonances and the J/
ψ meson production.
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.
Inclusive transverse momentum spectra of single electrons from Au+Au collisions have been measured at
S
N
N
=
130
GeV and 200 GeV at midrapidity by the PHENIX experiment at RHIC. After subtraction of ...background from photon conversions and light hadron decays, the spectra appear consistent with semileptonic decays of charmed particles.
We report on the observation of jet-like azimuthal and pseudorapidity correlations between the highest
P
T
photon (leading photon) and charged hadrons produced in both p-p and Au
Au collisions at
S
N
...N
=
200
GeV.
PHENIX has measured transverse momentum spectra of charged particles at mid-rapidity up to 10 GeV/c in Au+Au collisions at √s
nn
= 200 GeV. For central collisions, the yield at high
p
T
is ...significantly suppressed comparing to binary scaled p+p data, and this suppression is stronger than observed at 130 GeV 1,2. Above 4 GeV/c, the deficit of high momentum particles is almost independent of
p
T
.
PDF
