Summary
Some questions on the new unstable particles are discussed, with the deliberate avoidance of any very specific assumption. The slowness of the decay rates imposes, by semi-qualitative arguments, relevant restrictions. We try to develop fully such a viewpoint, and conclusions are drawn about production processes, about processes in which the excited hyperon takes part, and about processes which occur after the capture of a heavy meson or a hyperon by a nucleus. The important question is here to know what other independent assumptions must be added to that of the long mean lives to get a consistent scheme. The Λ0-nuclei are moreover analyzed from a more phenomenological standpoint. The implications of this analysis on the high spin model of the Λ0 are discussed. The arguments, of course, are not strictly quantitative; however their possible failure would be in any case an interesting conclusion. The possible composite nature of the new particles is briefly discussed in connection with the role of weak interactions and with the possible validity of charge independence at production. Charge independence at decay is not expected to hold and this question is discussed in the case of the θ0-meson.
Riassunto
Vengono discusse alcune questioni sulle nuove particelle instabili. Ci si aspetta, sulla base di argomenti qualitativi, che il fatto delle lunghe vite medie debba portare delle notevoli restrizioni circa gli altri processi. Possono così ricavarsi informazioni sui possibili processi di produzione e di interazione con i nucleoni. Se si cerca di sviluppare a fondo un tale punto di vista, sorge l’importante questione di sapere quali altri assunti indipendenti debbono venire aggiunti a quello delle lunghe vite medie per ottenere uno schema più completo e consistente. I nuclei Λ0 vengono discussi in maggiore dettaglio e soprattutto in connessione col modello a spin elevato del Λ0. Gli argomenti usati naturalmente non possono essere rigorosi e potrebbero anche risultare sbagliati; anche questa però sarebbe una indicazione importante. Infine vengono discussi l’eventuale ruolo delle interazioni deboli e la eventuale validità della charge-independence alla produzione. Ci si aspetterebbe che la charge independence non valga al decadimento e questo problema viene esaminato per il caso del mesone θ0.
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Gatto, R. Phenomenological study of the new particles. Λ-particles and Λ-nuclei. Nuovo Cim 1, 372–393 (1955). https://doi.org/10.1007/BF02855167
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DOI: https://doi.org/10.1007/BF02855167