Particle identification using cluster counting in a large drift chamber at normal conditions

Results on particle identification obtained measuring the primary ionization in a drift chamber operating in a mixture He 80%CH4 20% at normal conditions are presented. The data, collected at CERN (PS T9 beam), indicate that the cluster-counting technique allows a substantial improvement with respect to the more traditional measurements. πK separation of ⋍ 3.6σ at 4 GeV was obtained over the entire volume of the chamber: 144 (3 × 3) cm2 cells with an average tracks path length of 120 cm.