Three-particle correlations have been measured for identified pi(-) from central 158A GeV Pb+Pb collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body ...correlation has been found as expected for a mainly chaotic and symmetric source.
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.
A measurement of direct photon production in {sup 208}Pb+ {sup 208}Pb collisions at 158A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central ...collisions is extracted as a function of transverse momentum in the interval 0.5<p{sub T}<4 GeV/c . A significant direct photon signal, compared to statistical and systematical errors, is seen at p{sub T}>1.5 GeV/c . The result constitutes the first observation of direct photons in ultrarelativistic heavy-ion collisions. It could be significant for diagnosis of quark-gluon-plasma formation.
Disoriented Chiral Condensates (DCC) have been predicted to form in high energy heavy ion collisions where the approximate chiral symmetry of QCD has been restored. This leads to large imbalances in ...the production of charged to neutral pions. Sophisticated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects.
Recent results from the WA98 experiment Peitzmann, T.; Aggarwal, M.M.; Agnihotri, A. ...
Nuclear Physics A,
1999, Volume:
661, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
Recent results of the WA98 experiment with Pb induced reactions at 158.
A GeV are presented. The scaling properties of the transverse energy and the charged particle multiplicity at midrapidity with ...the number of participants is studied. Neutral pion spectra are compared to hydrodynamical parameterizations. The analysis of collective flow at target rapidity and at midrapidity is presented. The status of the study of direct photons and the search for isospin fluctuations is discussed.
We report on the design, construction, and test of a new gain monitoring system developed for the 10 000-module lead-glass calorimeter in the WA98 experiment. The system combines precision monitoring ...and modularity according to the general detector design. It is based on pulsed LEDs and photodiodes. The complete system was successfully used in an electron calibration and during the first Pb-ion beam time at the CERN SPS.
An integrated circuit for readout of particle detectors, producing a charge signal has been developed. The circuit contains 16 channels of charge integration, sample and hold amplifier, followed by ...an analog multiplexer. The charge content of each channel is digitized, one by one, by a 6 bit nonlinear flash ADC. The result is stored in a memory, pending for readout. The chip has proven to sense an input charge as low as 1 fC. Two versions of the chip exist, one with a gated charge integrator input and the other with a shaping amplifier input stage. Both circuits have been fabricated on large scale. They have successfully been used for readout of multistep avalanche chambers and streamer tube detectors in the Heavy Ion experiment WA98 at the CERN SPS.
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