Pion-nucleon cross-section for absorption and strange particle production at 6.1, 11.6 and 18.1 GeV/c

The Ecole Polytechnique one-meter heavy-liquid bubble chamber(1) was exposed at the CERN PS to 6.1, 11.6 and 18.1 GeV/c π− beams. Respectively 33 000, 10 000 and 29 000 pictures containing approximatively 4 pions per picture were taken. The liquid used was a mixture of 86% propane and 14% freon CF3Br by volume (68% propane and 32% freon by mass). The density of the liquid was 0.55, g/cm3, its radiation length 52 cm. From these pictures we have measured the absorption cross-section of negative pions in the heavy liquid and the cross-section for strange-particle production in the reactions: π−+(nucleon)→→(K+\(\bar K\)+nucleon)+nπ and π−+(nucleon)→(K+hyperon)+nπ.