C. Gruhn

Strangeness production at mid-rapidity in S + Pb collisions at 200 GeV/c per nucleon

Abstract Experimental evidence is presented for a source of unusually high strangeness content located at mid-rapidity in 200 GeV/ c per nucleon collisions of 32 S projectiles with a Pb target. The enhancement is not seen in p+Pb reactions measured in the same apparatus at the same energy. This source becomes dominant for central collisions.

Multiplicity Distributions in

Abstract The multiplicities of charged secondaries from inelastic αp and αα collisions have been measured using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. Corrected multiplicity distributions for αα and αp interactions are compared with those for pp interactions and with theoretical predictions.

\alpha \alpha

Abstract We have measured the longitudinal ( p L ) and transverse ( p T ) momentum distributions for p, d, t, and 3 He fragments in quasi-elastic alpha-alpha collisions at √ s = 125 GeV, using the upgraded Split-Field Magnet detector at the CERN Intersecting Storage Rings. The p T distributions reflect elastic scattering among the nuclear constituents as a main mechanism. The p L distributions are only weakly perturbed by this mechanism, and reflect mainly the internal (Fermi) motion of the nuclear constituents; their widths are consistent with expectations from statistical models.

and

Abstract Production of Λ, Λ , and K s 0 has been measured for a wide range of event multiplicity in S+Pb reactions at 200 GeV/c per nucleon. The production of Λ is shown to increase with multiplicity faster than expected from a superposition of p+p collisions. The effect is seen for low multiplicity (below 100 negative particles).

\alpha p

Two-particle rapidity correlations have been studied for αα, αp, andp p interactions at the CERN ISR using the Split-Field Magnet (SFM) detector. In order to isolate the true two-particle correlations, the analysis was performed at fixed charged multiplicity. In the framework of a simple cluster model, it is found that cluster widths as well as cluster multiplicities are the same for αα, αp, andp p interactions, and both decrease with increasing charged multiplicity.

Collisions at the {CERN} {ISR}

We analyse the variation of the average transverse momentum, 〈pT〉, with the multiplicity of charged particles produced in pp, pp, dd and αα collisions at ISR energies. An increase of 〈pT〉 with increasing particle density p=ΔnΔy for charged particles produced in the central region is observed. The energy dependence of this effect and its dependence on the type of colliding particles are discussed.

Momentum distributions of nuclear fragments in αα collisions at √s = 125 GeV

Abstract The yields of Λ, Λ , and Ξ−, Ξ + have been measured close to mid-rapidity in sulphur reactions on a Pb target at 200 GeV/c per nucleon beam momentum. Fully corrected production ratios of Λ Λ , Ξ + Ξ , Ξ − Λ and Ξ Λ are presented. The ratios have been analysed both in the context of a rapidly disintegrating quark-gluon plasma and a hadronic resonance gas. Our analysis shows that the hadron gas model is sufficient to explain the observed particle yields.

Multiplicity dependence of strangeness production in S + Pb collisions at 200 GeV/c per nucleon

Abstract Cross sections are measured for 16 O collisions with A1 and Pb. Dependences on beam momentum and atomic number are compared with data obtained at much lower beam momenta.

Two-particle rapidity correlations in αα, αp, andp p interactions at the CERN intersecting storage rings

Abstract Cross sections for charge changing and particle production are measured for 32 S collisions with Al, Fe, Cu, Ag and Pb targets at 200 GeV/ c . The measured difference between the two cross sections is discussed. Results are compared with data obtained with an 16 O beam.

Multiplicity dependence of transverse momentum spectra in pp,p̄p, dd and αα collisions at ISR energies

Abstract A new method is described for finding the primary vertex in a relativistic heavy-ion experiment with multiple nuclear targets. Due to the large number of tracks the use of an economic algorithm is essential. The method comes from system theory and is based on an application of the Kalman filter. The small uncertainty in the vertex position obtained provides a reliable target assignment for the interaction.