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

Results on particle identification obtained measuring the primary ionization in a drift chamber operating in a mixture He 804.014477nfo/METH/sub 4/ 20at 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. pi /K separation of approximately=3.6 sigma at 4 GeV was obtained over the entire volume of the chamber: 144 (3*3) cm/sup 2/ cells with an average track path length of 120 cm. (17 refs).