Summary
The Feynman, Gell-Mann model of weak interactions is modified by the introduction of neutral « currents », both of the strangenesss preserving (J) and strangeness changing (S) variety. The various currents, neutral and charged, are chosen and coupled in such a manner as to guarantee the |ΔT|=1/2 selection rule. TheJ currents, charged and neutral, are taken together to form an isotopic vector. The chargedS currents are taken to satisfy ΔS/ΔQ=+1. These conditions automatically impose on theS currents the property that they transform like the components of an isotopic spinor. The arbitrariness in the currents which remains at this stage is now removed by a definite choice, patterned after and meant to exploit Gell-Mann’s model of global symmetry for strong baryon-pion interactions. In so far as the latter constitutes a useful first approximation to strong interaction physics, we can make certain fairly definite and verifiable predictions concerning leptonic decay of hyperons, and notably: the protons in Σ+→p+π0 decay should be polarized in an opposite sense from those produced in Λ0→p+π− decay; and Ξ and Λ decays should show the same polarization properties. Presently known properties of Σ, Λ, and Ξ decays are well correlated in the present model.
Riassunto
Il modello di Feynman e Gell-Mann per le interazioni deboli è modifieato con l’introduzione di « correnti » neutre, sia della varietà (J) (conservazione della stranezza) sia della varietà (S) (variazione della stranezza). Le varie correnti, neutre e caricate, sono scelte ed accoppiate in modo da garantire la regola di selezione |ΔT|=1/2. Le correntiJ, cariche e neutre, sono prese assieme in modo da formare un vettore isotopico. Le correntiS cariche sono prese in modo da soddisfare la ΔS/ΔQ=+1. Queste condizioni impongono automaticamente alle correntiS la proprietà di trasformarsi come componenti di uno spinore isotopico. L’arbitrarietà delle correnti che rimangono in questo stadio viene ora eliminata con una scelta definita, delineata sul modello di Gell-Mann della simmetria globale per interazioni forti barione-pione e destinata a sfruttarlo. Poichè questa simmetria costituisce un’utile prima approssimazione alla fisica delle interazioni forti, possiamo fare alcune ben definite e verificabili previsioni sul decadimento leptonico degli iperoni, e principalmente: i protoni nel decadimento Σ+→p+π0 devono essere polarizzati in senso opposto a quelli prodotti nel decadimento Λ0→p+π−; i decadimenti Ξ e Λ devono presentare le stesse proprietà di polarizzazione. Le proprietà attualmente note dei decadimenti Σ, Λ e Ξ sono ben rappresentate da questo modello.
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References
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The results obtained below follow not from dynamical calculations but only from the symmetries which we have conjectured here in pursuit of a universal Fermi interaction model of all the weak interactions. These symmetries could of course be realized with alternative dynamical models. In particular, the present results on non-leptonic hyperon decay are obtained by B. d’Espagant andJ. Prentki:Phys. Rev.,114, 1366 (1959), who achieve the relevant symmetries with a direct coupling Hamiltonian. See alsoR. F. Sawyer:Phys. Rev.,112, 2135 (1958) andB. T. Feld (preprint). The present scheme is comprehensive in that the predictions concerning non-leptonic hyperon decay are tied to predictions concerning leptonic decay, to the |ΔT| = 1/2 rule, etc. It has therefore the possibility of being ruled out in a great variety of ways. I am indebted to Dr. B. d’Espagnat, Dr.B. Feld and Dr.A. Pais for interesting discussions on these points.
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M. L. Goldberger andS. B. Treiman:Phys. Rev.,111, 354 (1958).
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Work supported in part by the Office of Scientific Research, Air Research and Development Command.
Alfred P. Sloan Foundation Fellow.
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Treiman, S.B. Weak global symmetry. Nuovo Cim 15, 916–924 (1960). https://doi.org/10.1007/BF02860196
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DOI: https://doi.org/10.1007/BF02860196