J. Wickens

Some properties of the charged Σ hyperons

Abstract A sample of some 7500 K − meson captures at rest on hydrogen in emulsion giving rise to charged Σπ pairs has been used to determine r , the decay branching ratio of the Σ + hyperon, λ, the ratio of Σ − to Σ + hyperon production, τ Σ − , the lifetime of the Σ − hyperon, and C , the mean orbital capture time of Σ − hyperons in emulsion. The results obtained are r= σ + → n +π + all σ + decay modes = 0.484 ± 0.015, γ = σ − π + σ + π − = 2.34 ± 0.08, γ σ − = 1.41 +0.09 −0.08 × 10 −12 sec , and C 10 −12 sec.

A determination of the binding-energy values of light hypernuclei

Abstract The results of an experimental study of the binding energies of light hypernuclei are presented, based on a sample of 2008 uniquely identified π − mesonic decays. The problems of the calibration procedure and the selection criteria are discussed. Various aspects of the Λ -N interaction are reviewed in the light of these new results.

On the lifetime of the 3ΛH ypernucleus

The mean lifetime of the 3ΛH hypernucleus has been estimated in nuclear emulsion using the (π−+1H+2H) decays both at rest and in flight. The result, τ(3ΛH) = (1.28−0.26+0.35) · 10−10sec, is significantly lower than another recent experimental value [5] and the theoretical predictions. A possible explanation of the discrepancy with the theoretical predictions is briefly discussed.

Branching ratios for the π− mesonic decays of the hypernuclei Λ3H and Λ4H

Results are presented concerning the experimental determination, with large statistics, of the branching ratios for the π− mesonic decay of the hypernuclei Λ3H and Λ4H. The spin assignments J(Λ3H) = 12and J(Λ4H) = 0 are confirmed.

Evidence for the existence of particle-unstable states of the Λ12C and Λ14N hypernuclei

Abstract Evidence is presented for the existence of particle-unstable states of the Λ12C and Λ14N hypernuclei produced by the absorption at rest of K− mesons in light emulsion nuclei.

A measurement of the lifetime of the Λ5He hypernucleus

Abstract The mean lifetime of the Λ 5 He hypernucleus has been estimated in nuclear emulsion using the π − + p + 4 He decays both at rest and in flight. The result obtained is τ( Λ 5 He ) = (2.74 −0.50 +0.60 )·10 −10 sec. This result together with the experimental value of Q − , the ratio of the non-mesonic to π − mesonic decay rates for Λ 5 He, has been used to determine the ratio R = Γ( Λ 5 He → π − + p + 4 He )/Γ(Λ 0 → π − + p ) .

Final state interactions among the decay products of the hypernuclei Λ8Li and Λ12B

Abstract The results of a study of the decay of the Λ8Li and Λ12B hypernuclei are presented. The Λ 8 Li →π − + 8 Be ∗ →π − + 4 He + 4 He and Λ 12 B →π − + 12 C ∗ →π − + 4 He + 4 He + 4 He modes have been investigated in detail. New information on the decay mechanism of the 16.11 MeV state of 12C has been obtained.

A determination of the binding energy of the Λ13C hypernucleus

Abstract From the observation of 11 examples of the π − mesonic decay of Λ 13 C the binding energy of this hypernucleus is found to be 11.39 ± 0.15 MeV.

The question of the existence of a particle-stable Λ6Li hypernucleus

The recent reported evidence for the existence of the Λ6Li hypernucleus is questioned. No example of the (π−1H1H4He) decay mode of this hypernucleus was found in a sample of 7000 mesonically decaying hypernuclei.

The π+ mesonic decays of light hypernuclei

Twenty examples of π+ mesonic decays of light hypernuclei have been found together with 7000 π− mesonic decays. The ratio R4 of π+ mesonic decays for the gL4 He hypernucleus has been computed from the results of this work and those of a previous experiment [1] and is found to lie between the values 5.4 ± 1.5%1.7% and 6.9 ± 1.8%2.1%. The π+ mesonic decays of other species of hypernuclei are briefly discussed.