D. Hardtke

Mid-rapidity protons in 158A·GeV Pb+Pb collisions

Abstract Proton distributions at mid-rapidity (2 ≤ y ≤ 3) have been measured for 158A·GeV Pb+Pb collisions in the focusing spectrometer experiment NA44 at CERN. From baryon number conservation and by comparing the experimentally measured d N d y distribution with the transport model RQMD, we conclude that a rather high degree of nuclear stopping has been reached for the truly heavy-ion collisions at these energies. Transverse mass distributions exhibit characteristically thermal shapes and the slope parameters increase with the mass of the colliding system.

Three Pion Correlations in Sulphur Lead Collisions at the CERN SPS

Abstract π + π + π + correlations from sulphur-lead collisions at 200 GeV/c per nucleon are presented as measured by the focusing spectrometer of experiment NA44 at CERN. We have investigated the three-pion correlation function at mid-rapidity and found that a genuine three-body correlation is suppressed. A possible interpretation of this result is that the emission of particles is partially coherent.

Strange meson enhancement in PbPb collisions

Abstract The NA44 Collaboration has measured yields and differential distributions of K + , K − , π + , π − in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/ c Pb+Pb collisions at the CERN SPS. A considerable enhancement of K + production per π is observed, as compared to p + p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.The NA44 Collaboration has measured yields and differential distributions of K+, K-, pi+, pi- in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/c Pb+Pb collisions at the CERN SPS. A considerable enhancement of K+ production per pi is observed, as compared to p+p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.

One and two-dimensional analysis of 3π correlations measured in Pb+Pb interactions

Abstract π−π−π− correlations from Pb+Pb collisions at 158 GeV/c per nucleon are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. The three-body effect is found to be stronger for Pb+Pb than for S+Pb. The two-dimensional three-particle correlation function is also measured and the longitudinal extension of the source is larger than the transverse extension.

Coulomb effect in single particle distributions

Abstract Single particle distributions from heavy-ion collisions show the effect of Coulomb interactions on the final state. While a rather strong effect is seen in the ratio π − π + from central 158A·GeV/c Pb+Pb collisions, at most a small enhancement is found in the ratios from S+S and S+Pb collisions at 200A·GeV/c.

Particle ratios from central Pb + Pb collisions at the CERN SPS

We will address the physics of K?/K+ and /p ratios measured in 158 A GeV Pb + Pb collisions as a function of centrality and transverse momentum. We observe little significant centrality dependence in neither K?/K+ nor /p ratios and they are almost constant as a function of PT. In addition to the chemical freeze-out temperature Tch, we extract the chemical potentials for both light and strange quarks (?q and ?s) by comparing the present data with simple model predictions. Tch is greater than the thermal freeze-out temperature which is extracted from the transverse momentum distribution of charged hadrons.

Measuring the space-time extent of nuclear collisions using interferometry

Abstract Hanbury-Brown and Twiss (HBT) interferometry is used to study the space-time evolution of nuclear collisions at CERN energies. Pairs of identified pions, kaons and protons are studied by NA44 for a variety of collisions systems ranging from p-Pb to PbPb. The pion and kaon correlation data from the 1994 and 1995 Pb runs are compared to published data. The systematic increase in radius parameter with system size is continued in the Pb data sample. Model comparision stress the importance of scattering in the evolution of the collision.

One-, two- and three-particle hadron spectra — Recent results from CERN/SPS experiment NA44

Abstract Recent results of analyses on hadron spectra from the focusing spectrometer experiment NA44 are presented. One-, two- and three-particle hadron spectra in the mid-rapidity region at CERN/SPS energy have been measured. The mT inverse-slopes of proton and anti-proton in collision systems from p+A to Pb+Pb are discussed. Spectra of deuteron, triton and anti-deuteron are presented, and the flow effect on the composite particle spectra are discussed. The two-particle interferometry analysis is made for the π±π± and K+K+ correlations in the central Pb+Pb collisions, and the dependences of interferometric parameters on the transverse mass and the multiplicity are discussed.

Deuteron and triton production in Pb+Pb collisions at 158 A·GeV.

Abstract NA44 has measured the invariant cross section of deuterons and tritons at non zero p t in 158 A·GeV lead on lead collisions at CERN SPS. Normalized transverse mass spectra and coalescence parameters versus p t have been calculated showing a significant transverse flow. Radius parameters have been extracted using a simple thermal coalescence model. Results from RQMD+coalescence calculations are compared to the data.

Charged hadron distributions in pA and AA collisions at the CERN SPS

Abstract Single particle distributions of π ± , K ± , p , p and d near mid-rapidity from 450 GeV/c p A and 200 GeV/c per nucleon SA collisions are presented. Inverse slope parameters are extracted from the transverse mass spectra, and examined for indications of collective phenomena. Proton and antiproton yields are determined for different projectile-target combinations. First results from 160 GeV/c per nucleon PbPb collisions are presented.