$\Delta^{++}$ 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.