Summary
Strange particle production by 16 GeV/c negative pions in hydrogen has been studied. 60 000 pictures were taken with the CERN 32 cm hydrogen bubble chamber. The cross sections found for associated and K-K pair production are σyk= 1.32±0.15 mb, σk-k=2.21±0.25 mb. The angular distributions of the Λ0 and Σ+ hyperons show a pronounced backward peaking in the pion-proton c.m.s. The backward peak is less pronounced for Σ(−. The ratio Σ+/Σ− is 1.3 ±0.3 at production. The neutral kaons are significantly peaked forward. The average longitudinal momentum in the c.m.s. is 0.26±0.05 GeV/c along the direction of the incident pion. The average transverse momentum is small, ∼ 0.5 GeV/c, and possibly independent of the kind of particle produced. Our results indicate a higher mean value for Σ± than for Λ0 and K0. The average pion multiplicities are: for Y + K production 4.9 ±0.1, for K + -K production 4.0±0.1. The kinetic energy distributions have been compared with the predictions of the statistical theory. The contribution of nonstatistical processes is important. Different estimates give 30% as a lower limit.
Riassunto
Si è studiata la produzione di particelle strane con pioni negativi da 16 GeV/c in idrogeno. Si son prese 60 000 fotografie con la camera a bolle ad idrogeno da 32 cm del CERN. Le sezioni d’urto trovate per la produzione di YK associati e di coppie K-K sono σk-k = (1.32±0.15) mb, σYK= (2.21 ±0.25) mb. La distribuzione angolare degli iperoni Λ0 e Σ+ presenta un picco all’indietro nel sistema del centro di massa pioneprotone. Il picco all’indietro è meno pronunciato per i Σ-. Il rapporto Σ+/Σ- è 1.3±0.3 alla produzione. I kaoni neutri lianno un notevole picco in avanti. L’impulso longitudinale medio nel sistema del centro di massa è (0.26±0.05) GeV/c lungo la direzione del pione incidente. L’impulso trasversale medio è piccolo, ∼ 0.5 GeV/c, e forse indipendente dal tipo di particella prodotta. I nostri risultati indicano un valore medio più alto per Σ+- che per Λ0 e K0. Le molteplicità pioniche medie sono: perla produzione di Y+K 4.9±0.1, per la produzione di K+-K 4.0±0.1. Le distribuzioni della energia cinetica sono state confrontate con le predizioni della teoria statistica. Il contributo dei processi non statistici è importante. Valutazioni differenti danno 30% corne limite inferiore. ntίs|Traduzione a cura della Redazione.
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On leave from the Institute of Nuclear Research, Krakow.
On leave of absence from University of Stockholm.
On leave from the Institute of Nuclear Research, Warsaw.
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Bartke, J., Budde, R., Cooper, W.A. et al. Hyperon and kaon production by 16 GeV/c negative pions on protons. Nuovo Cim 24, 876–895 (1962). https://doi.org/10.1007/BF02751462
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DOI: https://doi.org/10.1007/BF02751462