Search for direct photons in p+Pb and p+C collisions at sqrt(sNN) = 17.4 GeV

Upper limits on direct photon production were determined as a function of the transverse momentum for 0.7 < pT <= 3.2 GeV/c with the WA98 experiment in p+C and p+Pb collisions at sqrt(sNN) = 17.4 GeV. The results are compared to direct photon measurements in Pb+Pb collisions at sqrt(sNN) = 17.3 GeV by WA98. Implications for a possible thermal direct photon contribution are discussed.Comment: 4 pages, 3 figures, to appear in the proceedings of the Quark Matter 2008 conference, Jaipur, India, 4-10 Feb 200

Δ++\Delta^{++} resonance measurements in a high multiplicity environment

The very large multiplicity of charged particles encountered in lead on lead collisions in the WA98 experiment at the CERN SPS provided new experimental challenges. Tracking detectors read out with high granularity were developed to achieve accurate position information in two dimensions, with the aim of reconstructing tracks with a minimum of combinatorial difficulties. A tracking system based on multi-step avalanche chambers equipped with a new electronic readout system was developed and implemented in the experiment during 1996. The different aspects of the tracking system and its performance are described. The extraction of the \Delta\sp{++} resonance from high statistics, high multiplicity samples of FRITIOF events has been studied in order to find a reliable method to reconstruct the number of produced \Delta\sp{++}. The first measurement on \Delta\sp{++} production in 158 A GeV Pb$+$Pb collisions, using the high resolution tracking system in WA98 is presented