The double differential multiplicities and rapidity distributions for Lambda hyperon production in central Au+Au interactions at AGS in the range of rapidities from 1.7 to 3.2 and the range of transverse kinetic energies from 0.0 to 0.7 GeV are parametrized in terms of the the Blast Wave approximation. The longitudinal and transverse radial expansion parameters and the mean temperature of Lambda hyperons after the freeze-out of the nuclear matter are presented. The predictions of the RQMD model with and without mean field potentials are compared to our data. Both variants of RQMD are parameterized in terms of the Blast Wave model and the results of such parameterizations are compared to the experimental ones. It is found that inclusion of the mean field potentials in RQMD is essential to account for the strong expansion observed in the data.
Directed flow of antiprotons is studied in Au+Au collisions at a beam momentum of 11.5A GeV/c. It is shown that antiproton directed flow is anti-correlated to proton flow. The measured transverse momentum dependence of the antiproton flow is compared with predictions of the RQMD event generator.
Asymmetric peaks in the pion-proton correlation functions were observed. Such an asymmetry indicates a displacement between the sources of the two particle species.
Directed flow of deuterons, tritons, $^3$He, and $^4$He is studied in Au+Au collisions at a beam momentum of about 10.8 $A$ GeV/c. Flow of all particles is analyzed as a function of transverse momentum for different centralities of the collision. The directed flow signal, $v_1(p_t)$, is found to increase with particle mass. This mass dependence is strongest in the projectile rapidity region.
Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, $v_2{2}$ and $v_2{4}$, for charged hadrons from U+U collisions at $sqrt{s_{rm NN}}$ = 193 GeV and Au+Au collisions at $sqrt{s_{rm NN}}$ = 200 GeV. Nearly fully overlapping collisions are selected based on the amount of energy deposited by spectators in the STAR Zero Degree Calorimeters (ZDCs). Within this sample, the observed dependence of $v_2{2}$ on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. An initial-state model with gluon saturation describes the slope of $v_2{2}$ as a function of multiplicity in central collisions better than one based on Glauber with a two-component multiplicity model.
Identified charged particle spectra of $pi^{pm}$, $K^{pm}$, $p$ and $pbar$ at mid-rapidity ($|y|<0.1$) measured by the $dedx$ method in the STAR-TPC are reported for $pp$ and d+Au collisions at $snn = 200$ GeV and for Au+Au collisions at 62.4 GeV, 130 GeV, and 200 GeV. ... [Shortened for arXiv list. Full abstract in manuscript.]
S. Ahmad
,B.E. Bonner
,S.V. Efremov
.
(1998)
.
"Nuclear Matter Expansion Parameters from the Measurement of Differential Multiplicities for Lambda Production in Central Au+Au Collisions at AGS"
.
Sergey V. Efremov
هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا