Hadronic spectra from interactions of Pb on Au at 158 AGeV/c have been measured by the CERES experiment at the CERN SPS. We report on preliminary results on transverse mass spectra of identified ...pions and negative hadrons as well as spectra of the positive charge excess obtained by subtracting the negative particle distribution from that of positive tracks. We have also performed a study of the event azimuthal anisotropies which give evidence for directed and elliptic flow in non-central collisions.
During the 1996 lead run time, CERES has accumulated 42 million events, corresponding to a factor of 5 more statistics than in 1995 and 2.5 million events of a special photon-run. We report on the ...results of the low-mass e
+e
−-pair analysis. Since the most critical item is the poor signal-to-background ratio we also discuss the understanding of this background, in absolute terms, with the help of a detailed Monte Carlo simulation. We show preliminary results of the photon analysis and summarize the results of the hadron analysis preliminarily reported on already at QM'97 1.
The CERES/NA45 experiment at the CERN-SPS is dedicated to study the production of e
+e
−-pairs in ultrarelativistic heavy ion collisions. Compared to extrapolations from results obtained in ...proton-induced reactions, it has previously observed an enhanced production in S-Au 1 and Pb-Au 2 collisions. To verify this enhancement and to study its properties, higher statistics were accumulated during a runtime in 1996. We report here, for the first time, on the results of this analysis (for details see ref. 3).
Light-particle emission from Au+Au collisions has been studied in the bombarding-energy range 100–250
A·MeV, using
ΔE−
E
R telescopes in coincidence with the FOPI detector in its
phase I ...configuration. Center-of-mass energy spectra have been measured for
Z = 1,2 isotopes emitted in central collisions at CM polar angles between 60° and 90°. Evidence for a collective expansion is reported, on the basis of the mean kinetic energies of hydrogen isotopes. Comparison is presented with statistical calculations (WIX code). For CM kinetic energy spectra, fair agreement is found between data and a recently developed transport model.
Using the FOPI facility at GSI Darmstadt complete data of Au on Au collisions at 150ital A MeV were collected for charged products (ital Z=1--15) at laboratory angles 1degreeleThetasub lable30degree. ...Central collisions were selected by applying various criteria. The kinetic energy spectra of fragments from an isolated midrapidity source are investigated in detail for center-of-mass angles 25degreeleThetasub c.m.le45degree. The heavy products (ital Zge3) are used to determine the collective energy which is found to be at least 10ital A MeV.
Charged particles have been observed in collisions of Au on Au at an incident energy of 150{ital A} MeV using a high-granularity detector system covering approximately the forward hemisphere in the ...center-of-mass system. Highly central collisions have been studied using a double selection criterion which combines large charged-particle multiplicities with small transverse-momentum directivities. In this class of events about one quarter of the total nuclear charge emerges as intermediate-mass fragments with nuclear charges {ital Z}{gt}2. These fragments are centered at midrapidity and are produced with large transverse velocities.
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