M. Lahanas

Neutral strange particle production in sulphur-sulphur and proton-sulphur collisions at 200 GeV/nucleon

AbstractThe production of Λ,

Pion and proton spectra in 32S + S collisions at 200 GeV/nucleon

\bar \Lambda

Study of the energy flow in sulphur-and oxygen-nucleus collisions at 60 and 200 GeV/nucleon

andKs0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in thep+S andp+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up topT=2 GeV/c.

Charged particle multiplicities in nuclear collisions at 200 GeV/N

The results on spectra of negative particles produced in16O+Au andp-Au collisions at 200 GeV/nucleon and16O+Au at 60 GeV/nucleon are presented. The correlations of average rapidity and average transverse momentum with event multiplicity are studied. Spectral shapes are similar for central16O+Au andp-Au collisions. The transverse momentum and rapidity distributions for central16O+Au andp-Au collisions differ strongly from corresponding distributions forp+p interactions. The FRITIOF model fails to describe the shapes of the transverse momentum distributions. The simple thermodynamical model of a single fireball does not fit the midrapidity transverse momentum distributions, and the rapidity distributions.

PION INTERFEROMETRY IN ULTRARELATIVISTIC NUCLEAR COLLISIONS

Abstract Rapidity spectra of pions and participant protons in S + S collisions at 200 GeV/nucleon are compared with N + N data. The average energy loss of the participating nucleons increases by 23% and is balanced by the energy of the final state particles, through a twofold increase of strange particle production and a similar enhancement, assumed for baryon-antibaryon pairs.

Multiplicity distributions in small phase-space domains in central nucleus-nucleus collisions

Results of a pion interferometry analysis are presented for the reactions S+C, S+S, S+Cu, S+Ag, S+Au and O+Au at 200 GeV per nucleon. Correlation functions were measured for pairs of negative pions in narrow windows of transverse momentum and rapidity, as a function of the three components of the momentum difference vector in cylindrical coordinates. The measured two-pion correlation functions suggest a space-time evolution of the system which proceeds in the following way for central nucleus-nucleus collisions. After interpenetration of the incident nuclei, the pion source expands in a boost invariant way along the collision axis. Estimates for the proper time interval between the onset of expansion and pion decoupling, as well as for the duration of pion emission are ∼ 4 fm/c and <2 fm/c, respectively. ThekT dependence observed forRS is consistent with the effect of resonance decays, alone or combined with slow transverse expansion. A linear dependence of the decoupling volume on the multiplicity is observed and indicates pion decoupling at a constant particle density. Presently available model predictions are briefly discussed

A new Coulomb correction method for Bose-Einstein correlations, based on the pi+pi- correlation measurements

We report on a systematic study of midrapidity transverse energy production and forward energy flow in interactions of16O and32S projectiles with S, Cu, Ag and Au targets at 60 and 200 GeV/nucleon. The variation of the shape of theET distributions with target and projectile mass can be understood from collision geometry. AverageET values determined for central collisions show an increasing stopping power for heavier target nuclei. A higher relative stopping is observed at 60 GeV/nucleon than at 200 GeV/nucleon. Bjorken estimates of the energy density reach approximately 3 GeV/fm3 in highET events at 200 GeV/nucleon with16O and32S projectiles. The systematics of the data and the shapes ofET and pseudorapidity distributions are well described by the Lund model Fritiof.

An investigation of intermittency in proton-gold, oxygen-gold, sulphur-gold and sulphur-sulphur interactions at 200 GeV per nucleon

Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.