N.K. Yamdagni

The stimulated decay of the Λ-hyperon

The relative strengths of proton stimulation ( LAMBDA -p) and neutron stimulation ( LAMBDA -n) non-mesonic decay interactions of A-hypernuclei were investigated by examining 19 observed examples of He-hyperfragments decaying in the non-mesic mode. The ( LAMBDA -p) interaction was observed to predominate over the (A-n) interaction by a ratio of 3.8 to 1, in excellent agreement with the expected ratio of 4 to 1. (H.D.R.)

The mass of the A0-hyperon

SummaryAn accurate determination of the A0-mass has been made using nuclear emulsion. From an analysis of 101 A0-decays, we obtain for the mass of the A0-hyperon, MA= (1115.46± 0.15) MeV andQA = (37.62± 0.14) MeV.RiassuntoAbbiamo eseguito un’accurata determinazione della massa del A0, usando emulsioni nucleari. Dall’analisi di 101 decadimenti A0 otteniamo per la massa dellïperone A0: MA=(1115.46±0.15) MeV e QA = (37.62±0.14) MeV.

Non-mesic decay of hypernuclei

A systematic study of hypernuclei, produced by K− and Σ− interactions in nuclear emulsion, and decaying in the non-mesic mode, is reported. The contaminations from the various background phenomena have been estimated and the sample is found to be reasonably pure. From the energy distribution of the decay products, a clear separation between the proton- stimulated and neutron-stimulated events has been obtained. The ratios of the proton to neutron stimulated decays for He-hyperfragments and for hyperfragments with charge ≥3 are determined as 3.8 and 2.5, respectively. These values are clearly greater than unity, and according to Ferrari and Fondas calculations, therefore, indicate that the stimulation process occurs predominantly when the hyperon is in the Λ-state. A model of the stimulation process is proposed. The non-mesic/mesic ratio Q as a function of the hyperfragment-charge is determined. The weighted mean Q (ΛHe) of the various emulsion works is obtained as 1.48±0.23. From this, the ratio |p|/|s| of the p and s channel amplitudes in Λ-decay is estimated to be 0.20−0.05+0.04.

Binding energies of the Λ0-hyperon in hypernuclei

Abstract An analysis of 29 hypernuclei produced by the interactions of K - -mesons and Σ - -hyperons in nuclear emulsion and decaying in the π - -mesic mode, is presented. Binding energies of the Λ 0 -hyperon in the hypernuclei Λ H 4 (6 events), Λ He 4 (4 events), Λ He 5 (9 events) and ΛLi 9 (1 event) are obtained as (2.37±0.30) MeV, (2.27±0.27) MeV, (3.27 ± 0.18) MeV and (7.75±0.80) MeV, respectively. The binding energies are derived from the Q Λ value determined in the same emulsion stack from which the hyperfragment data also originated. This makes the systematic errors in the binding energies negligible; the errors quoted are therefore only statistical. Besides the most commonly occuring decay mode of Λ He 5 , the rare decay mode Λ He 5 → He 3 +H 2 + π - has also been observed.

Concerning fore-aft asymmetry in Λ0-decay

SummaryA sample of Λ0-hyperons recorded in photographic emulsions has been identified by estimating the energy release,Q, in their decay. The observations have then been used to study fore-aft asymmetry in the decay of the Λ0-hyperon. The energy spectrum of Λ0-hyperons has allowed the fractions produced (a), by strong interactions: K−+→ →Λ0+π, Σ+→Λ0+; and (b), by radiative decay: Λ0→Λ0+γ, to be separately distinguished. In sample (a), the observed value of the quantityα

Binding energies of the ?0-hyperon in hypernuclei

\bar p

CONCERNING FORE-AFT ASYMMETRY IN /lambda/ -DECAY

=0.23±0.24, and ofNf/Nb=25/27, a result consistent with an isotropic distribution. For sample (b), the distribution is asymmetric,α