G. Claesson

MULTIPLICITY AND PSEUDORAPIDITY DISTRIBUTIONS OF CHARGED-PARTICLES FROM S-32 INDUCED HEAVY-ION INTERACTIONS AT 200-A GEV

Multiplicity and pseudorapidity distributions have been measured for32S+Al, Cu, Ag and Au at 200A GeV. The widths of the pseudorapidity distributions increase from central to peripheral collisions. The main contribution is assumed to come from the increasing fraction of charged particles stemming from the fragmentation of the target for peripheral collisions as compared to central collisions. On the average 170–180 charged particles per unit of pseudorapidity are attained for the most central32S+Au events at the maximum of the distribution. The target dependence of the yield of charged particles for central collisions is investigated. In the target rapidity region the yield is directly proportional to the target mass. The transverse energy per charged particle has been studied as a function of centrality and pseudorapidity. The experimental results are compared to the results from the Monte-Carlo model VENUS 3.11 which includes rescattering among secondaries. A comparison between different centrality triggers is made.

Upper limit for thermal direct photon production in heavy-ion collisions at 60 and 200A·GeV

The production of direct photons has been investigated in reactions ofp and16O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and π0 spectra have been measured in the pseudorapidity range 1.5≦η≦2.1 for the transverse momentum region 0.4 GeV/c≦pT≦2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of π0 and η mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed.

Fluctuations and intermittency in 200 A GeV 16O+(C, Au) reactions

Abstract Fluctuations in the pseudo-rapidity density of charged particles in 16 O+(C, Au) reactions at 200 A GeV were analyzed with the method of scaled factorial moments. The extracted moments are proportional to a power of the pseudo-rapidity bin size, which is consistent with intermittent behaviour. The dependence on target and on impact parameter are studied. The fluctuations are stronger for systems with fewer participating nucleons.

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 Differential cross sections for αα and αp scattering have been measured at √ s =125 and 88 GeV, respectively, in the t range from −0.2 to −0.8 (GeV/ c ) 2 using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. Comparison with theoretical calculations using the Glauber model confirms the importance of including inelastic shadowing effects in very high energy nucleus-nucleus elastic scattering.

and

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.

\alpha p

Abstract We present evidence for fluctuations of the average transverse momentum in pp, pα and αα collisions at ISR energies. In thermodynamical models, this is interpreted as fluctuations in the temperature of hadronic interactions. We find that the effect does not depend on the energy of the collision, however, the fluctuations are smaller for αp and αα reactions than for pp interactions.

Collisions at the {CERN} {ISR}

Charged pion yields and transverse energies of baryons are measured for the reaction16O+Cu, Ag, Au at 60 and 200A GeV bombarding energy in the target fragmentation region employing the Plastic Ball detector. Only little dependence of the measured quantities on the bombarding energy is found. The data are compared with the multi-chain fragmentation model of Ranft. As a result it turns out that a leading order formation zone cascade is not sufficient to explain the baryon yield and the transverse energies of baryons in the target fragmentation region.

Measurement of αα and αp elastic scattering 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 inclusive production of charged hadrons has been measured in αα and αp collisions at nucleon-nucleon c.m. energies (√s nn )of 31 and 44 GeV, respectively, for transverse momenta p T up to 5 GeV/ c in the central rapidity ( y ) region. at high p T the yields are consistent with being 4 times and 16 times highere than the ones in pp interactions at y =0, for αp and αα interactions, respectively. However, an enhancement over these factors, as expected from an earlier FNAL experiment, cannot be ruled out.