S Saini

A simple method of shower localization and identification in laterally segmented calorimeters

Abstract A method is proposed to calculate the first and second moments of the spatial distribution of the energy of electromagnetic and hadronic showers measured in laterally segmented calorimeters. The technique uses a logarithmic weightinh of the energy fraction observed in the individual detector cells. It is fast and simple requiring no fitting or complicated corrections for the position or angle of incidence. The method is demonstrated with GEANT simulations of a BGO detector array. The position resolution results and the c/gp separation results are found to be equal or superior to those obtained with more complicated techniques.

PRODUCTION OF SLOW SINGLY CHARGED FRAGMENTS IN 200 GEV/C HADRON NUCLEUS INTERACTIONS

Measurements of slow, singly charged fragments in the target rapidity region have been performed for proton and pion induced reactions with various nuclei at 200 GeV/c. Multiplicity, angular and energy distributions are examined and used to study the effects of rescattering in the nuclear medium. Data are compared to a “geometric cascade model” and to simulations with the VENUS 3.11 and the FRITIOF 1.7 Monte Carlo codes.

Azimuthal anisotropy in S + Au reactions at 200 A GeV

Abstract Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employd to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies.

Bose-einstein correlations in the target fragmentation region in 200A GeV16O+nucleus collisions

Correlations between positive pions are investigated in the target fragmentation region of 200A GeV16O+nucleus collisions. The pions are measured with the Plastic Ball detector in the WA80 experiment at the CERN SPS. The target mass dependence of the radii and the correlation strength extracted by interferometry is studied. A new approach to the fit of the correlation function is introduced. The correlation strength and both invariant and transverse radii increase with decreasing target mass. The transverse radius for16O+C reactions appears to be much larger than the geometrical radius of the nuclei involved. For the Au target only a small fraction of the measured pions contributes to the apparent correlation. Hints for a much larger second component in16O+Au reactions are observed. Rescattering phenomena may provide a clue to understand these phenomena.

Event by event measurement of 〈pT〉 of photons in S + Au collisions at 200 A·GeV

The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A.GeV from the ratio of the measured electromagnetic transverse energy (E-T(em)) to the photon multiplicity (N-gamma). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator

2-PROTON CORRELATIONS IN THE TARGET FRAGMENTATION REGION OF NUCLEAR COLLISIONS AT 200-A-GEV

Correlations between protons are studied in the target fragmentation region of reactions of protons and16O with C, Cu, Ag, Au and of32S with Al and Au at 200A GeV. The emitted protons were measured with the Plastic Ball detector in the WA80 experiment at the CERN SPS. The comparison of the correlation function with calculations, assuming a spherical, gaussian shaped source with a lifetime τ=0 fm/c, allows the extraction of radius parameters. The values are very close to those expected from the geometry of the target nuclei and increase with the target mass as αATarget1/3. Even in proton induced reactions the whole target nucleus is involved. The dependence of the radii on centrality, polar angleθlab, and energy, and their relation to measured proton yields are presented.

Emission of slow singly charged fragments in relativistic 16O-nucleus interactions☆

Multiplicity distributions of slow singly charged target fragments from O-16 induced reactions on C, Cu, Ag and Au are studied at 60 and 200 A GeV. The distributions from the two energies are essentially the same. Energy and angular distributions for slow protons are revealing the important role of cascading and rescattering in the spectator matter. The target dependence of the multiplicity of slow fragments exceeds A(T)2/3 for the heaviest targets.

Target fragmentation in proton and heavy-ion induced reactions at high energies

Results on pseudorapidity distributions, azimuthal correlations, and on two particle interferometry for identified protons and pions measured in the target fragmentation region of high energy proton-nucleus and nucleus-nucleus collisions are presented. Full participation of the whole target nucleus is observed even for 200 GeV p + Au collisions. Incorporation of strong rescattering phenomena into string models, including pion absorption effects in excited target matter, provides a good description of most experimental data.

COMPARISON OF PI(0) AND ETA-SPECTRA FROM S + AU COLLISIONS AT 200 GEV/C

Neutral pi0 and eta spectra have been obtained over a wide transverse momentum range for various centralities of S + Au collisions at 200 GeV/nucleon. The analysis was done of the full statistics of the WA80 experiment at CERN using the two-photon invariant mass spectra. Compared to the previous analysis [1, 2] the pi0 and eta spectra were obntained over an extended p(t) range of 0.2 <p(t)(pi0) <4.4 GeV/c and 0.4 <p(t)(eta) <3.0 GeV/c.

Effective source sizes of low rapidity soft particle emission

Abstract Correlations of positive pions and protons measured with the Plastic Ball detector in ultrarelativistic nucleus-nucleus collisions are studied. Source parameters are extracted for various projectile-target combinations. While the proton source can be explained by geometry, the pion source shows more subtle effects, which may be related to a very large source component. A comparison with the RQMD model for 200 A GeV 32 S + Au reactions reveals discrepancies for the pion source.