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Il Nuovo Cimento (1955-1965)

, Volume 5, Issue 6, pp 1700–1715 | Cite as

Systematics of Λ0 and θ0 decay

  • F. Eisler
  • R. Plano
  • N. Samios
  • M. Schwartz
  • J. Steinberger
Article

Summary

Systematic observations on 528 Λ00 production events in propane have yielded the following information: 1) There exists a neutral Λ0 decay; Λ0→π0 + n and the fraction of Λ0’s decaying in this mode is .32±.05. 2) The θ 1 0 component has a neutral decay mode, very probably θ 1 0 →θ00. The θ0 therefore very probably has even spin. The fractionP 1 0 → π0 + π0) /P 1 0 → 2π) is .14±.06. The branching ratioP0 → π0 + n) /P0 → π + n) is in good agreement with theI = 1/2 selection rule; the branching ratioP0 → 2π0) /P0 → π+ + π) seems to be in disagreement. 3) (51±7.5)%, or just one half of the θ0 mesons escape the chamber and are to be identified with the θ 2 0 -meson proposed byGell-Mann andPais (4). The question of the existence of additional (parity doublet) decay modes is discussed. 4) The decays Λ0 → μ + p + ν / e + p + ν are not observed and the fraction of such decays is less than 2%. 5) The 3 particle decay modes of the θ 1 0 have not been observed and are therefore very unlikely to exceed 2% of all θ 1 0 decays. 6) Preliminary measurements yield lifetimesτθ 1 0 =(.95 ± .08) · 10−10 s andτΔ0=(2.8 ± .2)·10−10 s. 7) For the θ 2 0 we obtain a lower limit of the lifetime, which together with the results ofLandeet al. (5) brackets the θ 2 0 lifetime (3 < θ 2 0 < 10)·10−8 s.

Riassunto

L’osservazione sistematica di 528 eventi Λ00 in propano ha dato i seguenti risultati: 1) Esiste un decadimento Λ0 neutro; Λ0 → π0 + n e la frazione di Λ0 che decadono in questo modo è .32±.05. 2) La componente θ 1 0 ha un modo di decadimento neutro, molto probabilmente θ 1 0 → π0 + π0. Il θ0 ha pertanto molto probabilmente spin pari. La frazioneP 1 0 → π0 + π0 /P 1 0 → 2π) è .14±.06. Il rapportoP0 → π0 + n)/P0 → π + n) è in buon accordo con la regola di selezioneI = 1/2; il rapportoP0 → 2π0) /P0 → π+ + π) sembra invece in disaccordo. 3) (51 ± 7.5)%, cioè, metà dei mesoni θ0 sfuggono dalla camera e si debbono identificare con i mesoni θ 2 0 proposti daGell-Mann ePais (4). Si discute l’esistenza di altri modi di decadimento (doppietto di parità). 4) I decadimenti Λ0 → μ + p + ν / e + p + ν non si osservano e la frazione di tali decadimenti è inferiore al 2%. 5) I modi di decadimento del θ 1 0 in 3 particelle non sono stati osservati ed è pertanto assai poco probabile che eccedano il 2% del totale dei decadimenti di θ 1 0 . 6) Misure preliminari danno vite medieτθ 1 0 = (.95 ± .08)·10−10 s eτΔ0 = (2.8±.2)·10−10s. 7) Per il θ 2 0 otteniamo per la vita media un limite inferiore che assieme ai risultati diLandeet al. (5) inquadra la vita media di tale particella fra (3 < θ 2 0 < 10)·10−8s.

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Copyright information

© Società Italiana di Fisica 1957

Authors and Affiliations

  • F. Eisler
    • 1
  • R. Plano
    • 1
  • N. Samios
    • 1
  • M. Schwartz
    • 2
  • J. Steinberger
    • 2
  1. 1.Nevis Cyclotron LaboratoryColumbia UniversityIrvington
  2. 2.Brookhaven National LaboratoryUpton

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