A SILICON ACTIVE TARGET FOR CHARM PARTICLE IDENTIFICATION

A silicon active target has been realized to reconstruct with high efficiency the primary vertex of heavy flavour photoproduction events in experiment E687 at the FNAL tevatron. The target is a telescope of 48 layers divided in 4 elements each, giving a total of 192 electronic channels read out with a preamplifier, an amplifier and a charge integrating ADC. The efficiency of the detector in identifying primary vertices has been measured to be congruent-to 80%, while the longitudinal resolution turned out to be sigma congruent-to 340-mu-m. Its level of performance allowed the use of the target as a powerful tool to select heavy quark events.