F. Posa

Negative Particle Production in Nuclear Collisions at 60-GeV/Nucleon and 200-GeV/Nucleon

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

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.

Recent results from experiment NA35

Abstract Enhanced strange particle production, nonstatistical multiplicity fluctuations and two-pion Bose-Einstein correlations were measured in O, S-nucleus reactions at 60 and 200 GeV/nucleon. The results indicate significant collective effects in high-energy nucleus-nucleus collisions.

PION INTERFEROMETRY IN ULTRARELATIVISTIC NUCLEAR COLLISIONS

Abstract Pion interferometry is the unique tool to study the space-time evolution of the systems created in the ultrarelativistic nuclear collisions. Five different data sets have been analyzed in terms of cylindrical coordinates, and all yield consistent results. We conclude that the system expands longitudinally, the decoupling proper time is ∼5 fm/c, the duration of particle emission is very short

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

Multiplicity distributions of negatively charged particles have been studied in restricted phase space intervals for central S+S, O+Au and S+Au collisions at 200 GeV/nucleon. It is shown that multiplicity distributions are well described by a negative binomial form irrespectively of the size and dimensionality of phase space domain. A clan structure analysis reveals interesting similarities between complex nuclear collisions and a simple partonic shower. The lognormal distribution agrees reasonably well with the multiplicity data in large domains, but fails in the case of small intervals. No universal scaling function was found to describe the shape of multiplicity distributions in phase space intervals of varying size.

Bose-Einstein correlations in ultrarelativistic heavy ion collisions

Abstract Results from the analysis of Bose-Einstein correlations of negative pions produced in central collisions of S + S, S + Ag, S + Au and O + Au at 200 GeV/N in a wide rapidity range 0.5

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

We present the measured correlation functions for π+π−, π−π− and π+π+ pairs in central S+Ag collisions at 200 GeV per nucleon. The Gamov function, which has been traditionally used to correct the correlation functions of charged pions for the Coulomb interaction, is found to be inconsistent with all measured correlation functions. Certain problems which have been dominating the systematic uncertainty of the correlation analysis are related to this inconsistency. It is demonstrated that a new Coulomb correction method, based exclusively on the measured correlation function for π+π− pairs, may solve the problem.

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

The intermittency phenomenon is investigated in proton-gold, oxygen-gold, sulphur-gold and sulphur-sulphur collisions at 200 GeV per nucleon. The data were taken with the NA 35 streamer chamber detector at the CERN SPS. The data samples are carefully corrected for double counting of tracks and for contamination from photon conversions, particle decays and secondary interactions. The analysis is carried out in terms of factorial moments, using a new definition, and of correlation integrals. Both methods show the presence of nonstatistical fluctuations (“intermittency”). The main conclusions are: The observation of the effect for pairs of hadrons with negative charges and its near absence for pairs of opposite charges is consistent with the assumption that Bose-Einstein correlations yield the dominant contribution. The “intermittency” effect is not proportional to (dn/dy)−1 which would be expected in superposition models. The measured relation between the second and third factorial moment for negative hadrons indicates that genuine 3-particle correlations are small. The predictions of a Monte Carlo simulation which is based on the Lund Fritiof model with the inclusion of Bose-Einstein correlations agree with the experimental results.

Production of charged kaons in central S + S and O + Au collisions at 200 GeV/Nucleon

Abstract Product of charged kaons in central S + S and O + Au collisions at 200 GeV/nucleon has been studied in the NA 35 Streamer Chamber experiment. Mean multiplicities and transverse mass distributions were obtained. They were compared with nucleon-nucleon data and with model predictions.

Study of particle spectra with an optically readout RICH detector in the NA35 experiment

Abstract The first identified particle spectra obtained with a proximity focusing RICH detector using an optical readout in the high particle density environment of heavy ion collisions at ultrarelativistic energies are presented. The rapidity and transverse momentum spectra of identified pions, kaons, and protons measured in the reaction SAu at 200 GeV/nucleon are shown and compared with the predictions of two event generators (Fritiof and VENUS).