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Zeitschrift für Physik A Hadrons and nuclei

, Volume 205, Issue 4, pp 409–419 | Cite as

Possible violation of the δSQ selection rule in leptonic decays of σ+-hyperons

  • F. Eisele
  • R. Engelmann
  • H. Filthuth
  • W. Föhlisch
  • V. Hepp
  • E. Kluge
  • E. Leitner
  • P. Lexa
  • P. Mokry
  • W. Presser
  • H. Schneider
  • M. L. Stevenson
  • G. Zech
Article

Abstract

We have found a possible example of the rare decayσ+→nΜ+Ν, which violatesδS=δQ. The positive decay track of theσ+ comes to rest in the hydrogen bubble chamber and decays into ane+. This track has all the characteristics of a stoppingΜ+. The decay neutron fortuitously scatters twice, producing two recoil protons. The only other possible interpretation of the event isσ+nγ(π+→Μ+Ν), where theπ+→Μ+Ν decay produces no deflection (θ<0.1 rad) and no significant change in curvature. Using thep-wave radiative decay predictions ofBarshay et al. we calculate that the integrated branching ratio for such “accidental” events isγ(σ+→nγ(π+→Μ stop + Ν))/γ(σ+→nπ+)=1.6×10−6.

Most of the contribution to this “accidental” branching ratio comes from radiative decays where theπ+ mesons have ranges less than 1 mm (pπ<20 MeV/c). If one excludes thoseΜ's with ranges less than 1.2 cm the above “accidental” branching ratio becomes 5.5×10−7. With this figure we estimate that we should have seen 6.5×10−2 events of this type thusfar in our experiment. The neutron momentum does not help in deciding between the two hypotheses. We therefore assign a confidence level of 7% for the radiative hypothesis. For the leptonic hypothesis we obtain an estimate of the branching ratio,γ(σ+→nΜ+Ν)/γ(σ+→nπ+)=5×10−5.

If one further accepts theσ+→nπ+Ν event reported byBarbaro-Galtieri et al. and theσ+→ne+Ν event reported byNauenberg et al., one obtains theδS=−δQ leptonic branching ratio [γ(σ+→nΜ+Ν)+γ(σ+→ne+Ν)]/γ(σ+→nπ+)=(4±3)×10−5.

Keywords

Hydrogen Elementary Particle Confidence Level Selection Rule Radiative Decay 

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Copyright information

© Springer-Verlag 1967

Authors and Affiliations

  • F. Eisele
    • 1
  • R. Engelmann
    • 1
  • H. Filthuth
    • 1
  • W. Föhlisch
    • 1
  • V. Hepp
    • 1
  • E. Kluge
    • 1
  • E. Leitner
    • 1
  • P. Lexa
    • 1
  • P. Mokry
    • 1
  • W. Presser
    • 1
  • H. Schneider
    • 1
  • M. L. Stevenson
    • 1
  • G. Zech
    • 1
  1. 1.Institut für Hochenergiephysik der Universität HeidelbergDeutschland

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