I. Otterlund

Centrality dependence of direct photon production in root s(NN) = 200 GeV Au+Au collisions.

The first measurement of direct photons in Au+Au collisions at {radical}(s{sub NN})=200 GeV is presented. The direct photon signal is extracted as a function of the Au+Au collision centrality and compared to next-to-leading order perturbative quantum chromodynamics calculations. The direct photon yield is shown to scale with the number of nucleon-nucleon collisions for all centralities.

On the correlation between fast target protons and the number of hadron-nucleon collisions in high-energy hadron-nucleus reactions

Abstract We present a simple model for high energy hadron-nucleus reactions, which describes how the number of fast target protons can be used as a measure of the number of hadron-nucleon collisions inside the target nucleus.

Nuclear interactions of 400 GeV protons in emulsion

Abstract We report on 400 GeV proton-emulsion nucleus reactions and compare the results to hadron-nucleus reactions at smaller energies. In particular we present results on the emission of fast target protons (essentially grey track particles) and on their correlation with the number of collisions inside the nucleus, ν, with the number of charged evaporated particles (essentially black track particles) and with the number of pions produced (essentially shower particles). We observe that the main features of the 200–400 GeV data are very similar. However, we find that the mean shower-particle multiplicity at 400 GeV is essentially higher than expected from the simple independent particle model prediction 〈ns〉 = 〈nch〉[1 + 0.5(〈ν〉 − 1)]. The shower particle multiplicities do not seem to follow a target mass dependence of the form 〈ns〉 = 〈nch〉 Aα with α = 0.14 or α = 0.19 as has been suggested in the literature. The pseudo-rapidity distribution shows limiting target and projectile fragmentation. The shower-particle multiplicity in the “central region” increases linearity with 〈ν〉 but faster than 0.5〈ν〉 times the corresponding multiplicity in pp reactions.

Forward and transverse energy distributions in oxygen-induced reactions at 60 A GeV and 200 A GeV

Abstract Results are presented from reactions of 60 A GeV and 200 A GeV 16O projectiles with C, Cu, Ag, and Au nuclei. Energy spectra measured at zero degrees and transverse energy distributions in the pseudorapidity range from 2.4 to 5.5 are shown. The average transverse energy per participant is found to be nearly independent of target mass. Estimates of nuclear stopping and of attained energy densities are made.

On slow particle production in hadron-nucleus interactions

A model for slow particle production in hadron-nucleus interactions is presented. The model successfully predicts correlations between the number of knock-on particles and the number of particles associated with the evaporation process as well as correlations with the number of collisions, ν, between the incident hadron and the nucleons inside the target nucleus. The model provides two independent possibilities to determine the number of primary intranuclear collisions, ν, i.e. by its correlation to the number of knock-on particles or to the number of evaporated particles. The good agreement indicates that the model gives an impact-parameter sensitive description of hadron-nucleus reactions.

Elastic and inelastic scattering of 1.03 GeV 12C projectiles

Abstract Elastic scattering cross sections of 86 MeV/N 12C ions on 12C, NATCa, 89Y and 208Pb targets has been measured together with inelastic scattering to the 4.4 MeV state of 12C. There is some indication for giant (quadrupole) resonance excitation in 40Ca. Optical model and DWBA analyses are reported. Nuclear transparency effect is discussed.

Saturation of azimuthal anisotropy in Au+Au collisions at root s(NN) = 62 – 200 GeV.

New measurements are presented for charged hadron azimuthal correlations at midrapidity in

Charged-particle distributions in 16O induced nuclear reactions at 60 and 200 A GeV

\mathrm{Au}+\mathrm{Au}

Scaling properties of charged particle multiplicity distributions in oxygen induced emulsion interactions at 14.6, 60 and 200 A GeV

collisions at

Projectile fragments from 86 MeV/nucleon 12C induced reactions

\sqrt{{s}_{NN}}=62.4