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The Λ 9 Li →π − + 9 Be ∗ →π − + p + 8 Li and Λ 9 B →π − + 9 C ∗ →π − + p + 8 B decay modes were investigated. The existence of an isospin - 3 2 state of 9Be, with excitation energy 18.6 ± 0.1 MeV and width Γ ≲ 300 keV has been established. From a reanalysis of European K− Collaboration emulsion data, new values of the binding energies of 9ΛLi and 9ΛB hypernuclei were found as 8.50 ± 0.12 MeV and 8.29 ± 0.18 MeV, respectively.

A study has been made of the decay sequence 12 Λ B → π − + 12 C ∗ → π − + 4 He + 4 He + 4 He . From a comparison of the measured branching ratios to certain states of 12C and the angular correlations observed in their decays with those predicted by Zieminska and Dalitz, it is concluded that the spin of the hypernucleus 12ΛB strongly favours the value of unity.

Kinematic analysis of simple hypernuclear production reactions has produced a sample of hypernuclei of ΛB, ΛC and ΛN with negligible background, and a much smaller sample of ΛBe. The values of the non-mesonic to π− mesonic ratio Q− for the above samples are 5.5 ± 0.5 and 4.3 ± 1.1, respectively. A sub-sample of 11ΛB hypernuclei was separated on the basis of production via an excited state of Λ12C, giving Q− = 4.8 ± 1.1 for Λ11B. Assuming the Fermi gas model is applicable to nuclei of mass A ≈ 11, two independent means of analysis of the non-mesonic decays give values for the Λ-neutron stimulation fraction n of 0.41 ± 0.09 and 0.34 ± 0.07 for hypernuclei of charge 5 ≦ Z ≦ 7.

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 masses of the charged Σ hyperons have been determined from the mean ranges of particles from the interactions of K− mesons at rest on hydrogen in emulsion, K− + p → Σ± + π∓, and also the mean rannge of the protons from Σ+ hyperons at rest, Σ+ → p + π0. The results are mΣ+ = 1189.39 ± 0.06 MeV/c2, mΣ− − mΣ+ = 7.91 ± 0.23 MeV/c2, which give mΣ−=1197.30±0.24 MeV/c2. The finding that the energy loss rate of low velocity negative particles is less than that of positive particles has been confirmed, but in contradiction with an earlier result, the range straggling for negative particles was not found to be anomalously high.

A new determination of the binding-energy values of the light hypernuclei ( A ⩽ 15) is reported, based on the analysis of some 27 000 π − mesonically-decaying hypernuclei produced by stopping K − mesons in nuclear emulsion. The results are combined with previous data obtained using similar experimental and analysis procedures.

A study has been made of the production of hyperfragments by the interactions of 800-MeV/c K- mesons in nuclear emulsion. The frequency of production, estimated to be 5.3±0.3%, is about the same as for K- mesons at rest. The hyperfragments are emitted predominantly in the forward direction and the ratio of nonmesonic to mesonic decays has been found to be 11.5±0.6, much greater than for K- mesons at rest. The proportion of hyperfragments of short range (range in emulsion

The analysis is reported of a sample of hypernuclei decaying non-mesonically with the emission of one or two charged particles which were obtained from K− meson captures at rest in nuclear emulsion. Making use of the decay parameters established for the 4ΛHe hypernucleus from observations in a helium bubble chamber, a value of Q−, the ratio of non-mesonic to π− mesonic decays, for λ5He together with the rates of certain decay modes have been determined.

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.

In this experiment the relative rates of production of charged Σ hyperons by the capture of K- mesons on neutrons and protons in the heavy (silver and bromine) and the light emulsion nuclei (carbon, nitrogen and oxygen) have been measured. From these results it is concluded that there is a large neutron excess present in the outermost regions of heavy nuclei.

A study has been made of the K− meson absorptions at rest in emulsion nuclei of the type K− + nucleus → π− + charged particle + hypernucleus. The existence of the particle unstable resonant state of the Λ12C hypernucleus, decaying via Λ 12 C → 1 H + Λ 11 B , has been firmly established. The excitation energy and natural width of this state are about 11 MeV and 0.4 MeV respectively.

Among 1148 K/sup -/ stars observed in an IIford K5 stack, 390 pi - mesons and 12 doubtful pi -mesons were found. A pi /K/sup -/ ratio of STA39.2 + 1.3 plus or minus 2!% is given, higher than previous results. This value is subject to statistical fluotuations, errors in solid angle correction, and observational loss. Comparison with previous work shows that the scanning loss was chiefly among high-energy pi -mesons in K sigma /sub 1/ stars and multi- pronged events. This implies a larger proportion of LAMBDA /sup 0/ mesons produced in K/sup -/ + N interactions, and that pi -meson absorption is smaller than estimated. (T.R.H.)

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) = 1 2 and J(Λ4H) = 0 are confirmed. © 1970., SCOPUS: ar.j, info:eu-repo/semantics/published

The emission of hyperfragments and the formation of cryptofragments following the absorption at rest of Σ- hyperons in emulsion nuclei have been studied. Both these phenomena appear to occur less frequently than in the case of K- mesons absorptions. From of a study of short prongs and Auger electrons it is suggested that hyperfragments are emitted predominantly from light nuclei, while cryptofragments are formed preferentially in heavy nuclei. © 1962 Società Italiana di Fisica., SCOPUS: ar.j, info:eu-repo/semantics/published

A study has been made of the production of hyperfragments by the interactions of K−-mesons of 3.0 and 5.0 GeV/c momentum in nuclear emulsion. The observed frequencies of production, (3.0±0.1)% and (2.2±0.1)% respectively, are significantly smaller than at lower K−-meson momenta, while the range distributions show a relative increase in the number of hyperfragments of range greater than 5 µm. This increase is attributed to a larger contribution from the fragmentation process, which is especially significant at intermediate ranges [(10÷50) µm], and to greater mean ranges for the heavy hyperfragments, which broaden the peak at short ranges (⩽10 µm). The hyperfragments of range less than 10 µm are mainly heavy residual products of silver and bromine nuclei; their mass numbers differ on the average from those of the parent nuclei by about 30 and 35 nucleon masses for 3.0 and 5.0 GeV/c interactions respectively. Eight examples of π− mesonic decays of heavy hyperfragments, and one probable example of a double hyperfragment, have been observed.

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.

The evidence concerning the region of the nucleus in which the capture of K − mesons in K mesonic atoms predominantly occurs is re-examined in the light of a recent criticism. It is concluded that capture in the extreme peripheral region where the nuclear density is of the order of 5 per cent of the the central density and the existence of a neutron halo in heavy nuclei remain the most probable interpretation of the available data.

An apparent variation of the mass of the Λ-hyperon with the energy of the decay π--meson has been observed in emulsion. This anomaly has been attributed to a systematic error in the range-energy relation for emulsion for particle velocities greater than 0.6 c. © 1970 Societa Italiana di Fisica.

The possibility of the existence of an isomeric state of Λ 7 Li is considered. The conclusion appears to depend crucially on the energy of the excited state 5 2 + of Λ 7 Li. If only the spin-dependent central Λ-N forces are taken into account to explain the splitting of the states in hypernuclei then different values of parameter Δ for different states have to be considered. Tensor and spin-orbit forces might contribute to the explanation of the apparent changes of Δ for different p-shell hypernuclei in their ground and excited states.

In a sample of approximately 11 000 hypernuclei obtained from K−-meson captures at rest in nuclear emulsion, eleven examples of the π+-mesonic decay of hypernuclei have been observed. From the ten which are attributed to the decay of4HeΛ, a value of (9±3)% is obtained forR, the ratio of π+ to π− mesonic decays for this hypernucleus. This result is larger than both that previously found experimentally and that predicted theoretically.

A stack of nuclear emulsion pellicles of total volume 10 litres was placed, together with two spark chambers in the neutrino beam of the CERN proton synchrotron. The tracks of secondary particles from neutrino interactions in the emulsion were observed in the spark chamber. The spark chamber tracks were used to locate the tracks produced by the same particles in the emulsion. These tracks were then followed back in the emulsion to the neutrino interaction in which they originate. Of a total of seven neutrino interactions expected to be produced in the emulsion stack during this exposure four were located in this way and their characteristics studied.

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.

Further examples of the π− mesonic decay of Λ 7 Be , Λ 10 B and Λ 11 B hypernuclei are reported. The binding energy values obtained in this work are combined with previous results.

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.

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.

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.

The existence of the hypernucleus 8ΛHe has been established with the Λ-hyperon separation energy BΛ = 7.16 ± 0.70 MeV.

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 ) .

A total of 3,480 K/sup -/-mesons were observed. Of these, 445 interact in flight, at a mean energy of 40 Mev and only their general characteristics were studied. Little difference was observed between the number of unstable charged particles ( SIGMA plus or minus -hyperons and pi plus or minus -mesons) in these interactions and those in the 3,035 interactions at rest. The 3,035 K/sup - /-interactions at rest were studied in detail. The results on those interactions in which pi -mesons are emitted are given. An estimate of the SIGMA -hyperon nuclear potential is based on the energy spectrum of pi -mesons emitted in the K/ sup -/-interactions in which the only charged particles emitted are a pi meson and a SIGMA -hyperon. A detailed examination of ihe angular distribution of 2- pronged events, and of the sign ratio of the pi -mesons, the prong distribution and energy release in all events led to an estimate of the probabilities of absorption of positive and negative SIGMA hyperons in the parent nucleus, and to a partition of the events between the various primary reactions. (auth)

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.

SCOPUS: ar.j, info:eu-repo/semantics/published

Low-energy K/sup -/-p elastic scattering events in bubble chambers and emulsions are studied in order to investigate the possibility of a peak at approximately 30 Mev. The results indicate that the scattering cross section is increasing in the region of lowest K/sup -/ meson momentum and that there is only approximately 1O% probability that the cross section will flatten off at momenta lower than 120 Mev/c. Possible explanations are offened for the cross-section flattening observed in earlier emulsion experiments. (D.L.C.)

Evidence for the existence of a particle-stable state of the 6 Λ He hypernucleus is presented.

Seventeen litres of nuclear photographic emulsion have been exposed to the wide-band neutrino beam at Fermilab. Tracks of secondaries from neutrino interactions in the emulsion were observed in a wide-gap spark chamber and a system of narrow-gap spark chambers and counters down beam. From measurements on the tracks in the wide-gap chamber the positions of vertices from which the secondaries diverged were predicted and 37 neutrino interactions in emulsion were located. Factors affecting the efficiency of location of events searched for (approx.20% in this experiment) are assessed and conclusions drawn about means of optimizing the design of experiments employing emulsion hybrid techniques. In one of the interactions a secondary track gave rise to three tracks after a distance of 182 ..mu..m. Further measurements made on this event do not alter the previous conclusion of its most likely interpretation as the decay of a short-lived particle of lifetime approx.6 x 10/sup -13/ sec.

Result are presented of an emulsion study of the low energy part of the π+ spectrum (1 MeV < Tπ < 30 MeV) resulting from 4639 τ′ decays of K+ mesons at rest. Contrary to the findings of Davison et al. this experiment shows no evidence for the existence of the σ(π0π0) resonant state, there being no lack of events at the lowest energies. The spectrum is analysed in terms of a standard polynomial development of the decay matrix element. © 1976., SCOPUS: ar.j, info:eu-repo/semantics/published

A systematic search has been made for decays of A0-hyperons around 5262 interactions of K--mesons at rest in photographic emulsion. From the 41 decays of correlated A0-hyperons observed in this sample, it has been estimated that (47±7)% of all K--meson interactions at rest in emulsion nuclei emit neutral hyperons. On consideration of the conservation of strangeness it is suggested that cryptofragments are formed in (30±7)% of all such K--meson absorptions and that the non-mesonic decays of these cryptofragments give rise to a considerable proportion of the protons of energies greater than 60 MeV emitted from K--meson captures. © 1961 Società Italiana di Fisica., SCOPUS: ar.j, info:eu-repo/semantics/published

In this study of hyperfragment production by K--meson absorptions at rest in emulsion nuclei, an attempt has been made to estimate the contribution of heavy spallation hyperfragments to the total observed number. In a sample of 24 640 K--meson captures, 1612 secondary events have been attributed to the production and subsequent decay of hyperfragments. From a study of the characteristics of both the production and decay disintegrations, it is concluded that about one half of the observed hyperfragments consists of λ0-hyperons trapped in the heavy spallation products of silver and bromine and these are almost entirely confined to the (0/3) μm range interval. The consequences of their presence aie discussed.

The detailed analysis is presented of an event which is interpreted as the mesonic cascade decay of a double hyperfragment produced by the capture of a Ξ- hyperon on a light emulsion nucleus. The most likely interpretations of the double hyperfragment are those in terms of either ΛΛBe10 or ΛΛBe11. © 1963., SCOPUS: ar.j, info:eu-repo/semantics/published

SCOPUS: ar.j, info:eu-repo/semantics/published