Omega- and Omega+ production in central Pb + Pb collisions at 40 and 158A GeV

Results are presented on Omega production in central Pb+Pb collisions at 40 and 158A GeV beam energy. For the first time in heavy ion reactions, rapidity distributions and total yields were measured for the sum Omega(-) + Omega(+) at 40A GeV and for Omega(-) and Omega(+) separately at 158A GeV. The yields are strongly underpredicted by the string-hadronic UrQMD model but agree better with predictions from hadron gas models.     

Antiproton production in nucleon-nucleus and nucleus-nucleus collisions at the CERN-SPS

A model for antiproton production in nucleon-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon, based on the Wounded Nucleon Model is developed. The predictions are compared to published nucleon-nucleus and sulphur-nucleus data. The results suggest the presence of similar antiproton production processes in nucleon-nucleus and nucleus-nucleus collisions near midrapidity.     

Further development of a model for the production of strange particles in nucleus-nucleus collisions

A previously proposed model for the production of neutral strange particles in nucleus-nucleus collisions, based on the Additive Quark Model and nuclear cascading, is further developed. The model predictions on neutral strange particle multiplicities, transverse momentum and rapidity distributions are compared with the existing oxygen- and sulphur-nucleus data at 200 GeV per nucleon. The predictions for central PbPb collisions are presented and discussed in some detail.     

Inclusive production of charged kaons in p+p collisions at 158 GeV/c beam momentum and a new evaluation of the energy dependence of kaon production up to collider energies

New data on the production of charged kaons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The kaons are identified by energy loss in a large TPC tracking system. Inclusive invariant cross sections are obtained in intervals from 0 to 1.7 GeV/c in transverse momentum and from 0 to 0.5 in Feynman x. Using these data as a reference, a new evaluation of the energy dependence of kaon production, including neutral kaons, is conducted over a range from 3 GeV to $\mathrm{p}+\overline{\mathrm{p}}$ collider energies.     

Dynamical fluctuations in the hadronic temperature

A density two-point correlation function calculation and a power-spectrum analysis of non-statistical event-by-event fluctuations in the mean transverse momentum at large multiplicityn is performed. Good agreement with the data ofK. Braune et al. is obtained if thep _t-density function of the exponential form in the transverse mass with an event-by-event fluctuating slope is used. The pattern of the fluctuating slope is Gaussian with the mean determined by the data on \(\left\langle {\bar p_t (n)} \right\rangle \) for eachn, and the normalized standard deviation as the only free parameter taken to be 0.68. In thermodynamical models, the slope fluctuations may be interpreted as fluctuations in the temperature of the hadronic system.     

Evidence for the constant-matrix-element mechanism in the breakup of the3He+7Li system and highly excited states in6Li

The inclusive alpha particle spectra from the breakup of the³He+⁷Li system atE ³He=42.9 MeV are analyzed in the frame of the nuclear reaction model whose matrix element does not depend on the relative energies of the outgoing particles and is therefore constant. The comparison with a recent analysis of thep+⁹Be interaction, leading to the same composite system, has shown the correlation of the final-state configuration on the entrance-channel cluster structure.the existence of broad excited states for⁶Li excitation energies between 19 and 28 MeV is confirmed.     

System-size dependence of strangeness production in nucleus-nucleus collisions at squareroot[sNN]=17.3 GeV

Emission of pi+/-, K+/-, phi, and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S, and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size.     

Event-by-event fluctuations of the Kaon-to-Pion ratio in central Pb+Pb collisions at 158 GeV per nucleon

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.