K
−/K
+ and
p
¯
/
p
ratios measured in 158 A·GeV Pb+Pb collisions are shown as a function of transverse momentum
P
T
and centrality in top 8.5% central region. Little centrality dependence of the
K
...−/
K
+ and
p
¯
/
p
ratios is observed. The transverse mass
m
T
distribution and
dN/dy of
K
+,
K
−,
p and
p
¯
around mid-rapidity are obtained. The temperature
T
ch
and the chemical potentials for both light and strange quarks (μ
q, μ
s) at chemical freeze-out are determined by applying simple thermodynamical model to the present data. The resultant μ
q, μ
s and
T
ch
are compared with those obtained from similar analysis of SPS S+A and AGS Si+A data. The chemical freeze-out temperature
T
ch
at CERN energies is higher than thermal freeze-out temperature
T
fo
which is extracted from
m
T
distribution of charged hadrons. At AGS energies
T
ch
is close to
T
fo
.
Hanbury-Brown and Twiss (HBT) interferometry is used to study the space-time evolution of nuclear collisions at CERN energies. Pairs of identified pions, kaons and protons are studied by NA44 for a ...variety of collisions systems ranging from p-Pb to PbPb. The pion and kaon correlation data from the 1994 and 1995 Pb runs are compared to published data. The systematic increase in radius parameter with system size is continued in the Pb data sample. Model comparision stress the importance of scattering in the evolution of the collision.
The invariant differential cross section for inclusive electron production in p+p collisions at root 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(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(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(c (c) over bar) = 0.92 +/- 0.15(stat) +/- 0.54(syst) mb.
The NA44 experiment has measured single-particle inclusive spectra for charged pions, kaons, and protons as a function of transverse mass near midrapidity in 158A GeV/c Pb+Pb collisions. From the ...particle mass dependence of the observed m(T) distributions, we are able to deduce a value of about 120 MeV for the temperature at thermal freeze-out. From the observed ratios of the rapidity densities, we find values of the chemical potentials for light and strange quarks and a chemical freeze-out temperature of approximately 140 MeV.
J/psi production has been measured in proton-proton collisions at roots=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. ...Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mub. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.
Recent results of analyses on hadron spectra from the focusing spectrometer experiment NA44 are presented. One-, two- and three-particle hadron spectra in the mid-rapidity region at CERN/SPS energy ...have been measured. The
m
T
inverse-slopes of proton and anti-proton in collision systems from p+A to Pb+Pb are discussed. Spectra of deuteron, triton and anti-deuteron are presented, and the flow effect on the composite particle spectra are discussed. The two-particle interferometry analysis is made for the π
±π
± and
K
+
K
+ correlations in the central Pb+Pb collisions, and the dependences of interferometric parameters on the transverse mass and the multiplicity are discussed.
We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at MathML equation using the STAR ...detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage -1.3,1.3. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes.
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