Search

The radiativeΣ+ → nπ+γ decay mode was analysed in the 81 cm SACLAY hydrogen bubble chamber exposed to a stoppingK− beam at the CERN PS. The pion spectrum was measured up to momenta of 150 MeV/c in theΣ rest frame.

The decay modesΣ±→nπ±γ, Σ+→pγ,Σ+→pe+e}- were studied in the 81 cm Saclay hydrogen bubble chamber. In the radiative decayΣ±→nπ±γ only low momentum pions which stop in the chamber were accepted.

All experimental data on leptonic decays of Baryons available after the Kiev Conference on High Energy Physics (Sept. 1970) are used to fit the parameters of the Cabibbo theory. Especially new results on σ− and Λ leptonic decays and the values of the Σ± lifetime are included.

In a bubble chamber experiment about 2×106Σ±-decays have been measured to separateΣ±→ne±¯ν events from the two-body modes. NoΣ+→ne+ν event was found whereas 607Σ−→ne−¯ν decays could be identified. The data yield for the ΔQ=−ΔS decay an upper limit: $$\frac{{\Gamma \left( {\sum {^ + } \to ne^ + v} \right)}}{{\Gamma \left( {\sum {^ - } \to ne^ - v} \right)}}< 1.9 x 10^{ - 2} (90\% confidence level)$$ and the branching ratio: $$\frac{{\Gamma \left( {\sum {^ - } \to ne^ - v} \right)}}{{\Gamma \left( {\sum {^ - } \to n\pi ^ - } \right)}} = (1.09 \pm 0.06) x 10^{ - 3} .$$