Summary
A model to describe the production of cascade particles in Kp collisions is set up in which the pole contribution of the λ and Σ particles and the contributions of two-particle intermediate states are considered. These latter states are approximated by Y* resonances in thes andu channels and by a D -particle or resonance, a boson of strangeness 2, in thet channel. The two alternatives of spin 1/2 and spin 3/2 θ are considered. A field-theoretical technique is used in which all spin f states are described by the Rarita-Schwinger formalism. The differential and total cross-sections for the production process are calculated at various energies for all possible parity combinations. A comparison with the experimental data indicates that the spin of the cascade particle is not 3/2. The production process is anti-peripheral in the sense that the dominant mechanism is fermion exchange in theu channel. The data can best be fitted by the parity combinations P(λΣ) even, P(KλN) odd and P(Kλθ) odd. In this case it is also required that gkλngkλθ t~ gKΣNg kΣ θ. There is also some evidence for a peripheral process mediated by a D-particle or KK resonance. The analysis indicates that such a state, with isospin 1, should have spin 0 and even parity. The mass cannot be established but a mass of 1000 MeV and a width of 130 MeV is consistent with cascade production in both Kp and pp collisions.
Riassunto
Per descrivere la produzione di particelle in cascata nelle collisioni Kp si costruisce un modello in cui si prendono in considerazione i contributi del polo delle particelle λ e Σ ed i contributi degli stati intermedi di due particelle. Questi Ultimi stati sono approssimati con risonanze Y* nei canali s edu e con una particella o risonanza D, un bosone di stranezza 2, nel canalet. Si prendono in considerazione le due alternative di un θ di spin 1/2 o di spin 3/2. Si usa una tecnica di teoria dei campi in cui tutti gli stati di spin f sono descritti dal formalismo di Rarita-Schwinger. Si calcolano le sezioni di urto totali e difierenziali per il processo di produzione a varie energie per tutte le possibili combinazioni di parità. Un confronto con i dati sperimentali indica che lo spin della particella della cascata non è 3/2. Il processo di produzione è anti-periferico nel senso che il meccanismo predominante è uno scambio di fermioni nel canaleu. Si possono approssimare meglio i dati con le combinazioni di parità P(λΣ) pari, P(KλN) dispari e P(Kλθ) dispari. In questo caso si richiede anche che gKλNgKλθ≈ ≈gkΣNgkΣθ. Si ha anche qualche prova di un processo mediato da una particella D ossia risonanza KK. L‘analisi indica che tale stato, di isospin 1, deve avere spin zero e parità pari. Non se ne puÒ stabilire la massa ma una massa di 1000 MeV ed una ampiezza di 130 MeV concordano con la produzione in cascata nelle collisioni Kp e pp.
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The research reported in this document has been sponsored in part by the Air Force Office of Scientific Research, OAR, through the European Office, Aerospace Research, United States Air Force.
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King, R.C. Production of cascade particles. Nuovo Cim 30, 1220–1244 (1963). https://doi.org/10.1007/BF02828783
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DOI: https://doi.org/10.1007/BF02828783