Etude à 1.15 GeV/c de la création associée π+ + p → Σ+ + K+

Riassunto Abbiamo analizzato 78 eventi di produzione associata π+ + p→ Σ+ + K+, per mezzo di una camera a bolle a propano (40 cm x 20 cm x 20 cm) posta in un campo magnetico di 12.7 kG. H fascio usato aveva un impulso di (1.155±0.025) GeV/c ed aveva la seguente composizione: π+ ;P :Μ+ :e+ -100: 10;8 : 1. Abbiamo ottenuto i seguenti risultati: 1) le sezioni d’urto totale(Σ (0.214±0.035) mb) e differenziale ottenute si accordano con l’ipotesi della indipendenza della carica; 2) per gli eventiΣ+(π+n) non ho trovato significative asimmetrie sopra-sotto, destra-sinistra od avanti-indietro; 3) la vita media del τ=(0.75 −0.09 +0.13 )⋅10−10s Summary 78 associated production events Σ-+ p → Σ++ K+ have been investigated by means of a propane bubble chamber (40 cm x x 20 cm x 20 cm) placed in a magnetic field of 12.7 kG. The beam used had a momentum of (1.155±0.025) GeV/e, and had the following composition: π+:pπ+:e+. We have obtained following results: 1) The total (Σ (0.214±0.035) mb) and differential cross sections obtained are in agreement with the charge independence hypothesis; 2) for Σ+(π+n) events, no significant asymmetries, up-down, right-left or forward-backward, were found; 3) the mean life of Σ+ is τ=(0.75 −0.09 +0.13 )⋅10−10s.