L. Majling

Supermultiplet structure and decay properties of hypernuclear 1+ resonances in Λ6Li

Abstract The excitation function for the 0 ℏω and 1 ℏω levels of Λ6Li, populated in the (K−, π−) reaction at ϑ π= 0°, is calculated in the framework of the translationally invariant shell model. One-baryon and cluster widths for the decay of resonance hypernuclear states are estimated. The decay properties of those states are shown to be essentially given by the Young tableaux selection rules. Very good agreement with recent experimental data at pK = 790 MeV/c at CERN is achieved. The decay of Λ 6 Li ∗ into exicted Λ 4 He ∗ ( Λ 4 H ∗ ) with subsequent hypernuclear γ-emission is discussed as well.

WAVE FUNCTIONS FOR MIXED CONFIGURATIONS AND THE RACAH ALGEBRA OF SU(4).

Abstract A new method of construction of many-nucleon wave functions with a given Young tableau for two unfilled shells is described. The Racah algebra of the group SU(4) is employed for obtaining the many-particle coefficients of fractional parentage as well as calculations of matrix elements of one- and two-particle operators.

Effective λN-interaction and spectroscopy of low-lying states of 1p-shell hyernuclei

A new set of the shell-model two-particle potential parametersδ,SΛ,SN andT forp-shell hypernuclei is proposed. The set is consistent with the available data on the excited levels ofΛ7Li,Λ9Be,Λ10B,Λ12B andΛpO. The classification of low lying states andγ-transitions in the 1p-shell hypernuclei is discussed in terms of the {s4pn*sΛ:JT} configurations. The feasibility for the excited bound states and for theγ-transitions to be observed in the spin-flip and non spin-flip single-nucleon reactions is examined in detail.

On nucleon decays of hypernuclear resonances — Population of bound hypernuclear levels

Abstract Hypernuclear resonances excited in ( K − ,π 0 ) reactions decay also via the nucleon channel and the low lying part of hypernuclear spectra is thus populated. The analysis — quantitative for A = 14- suggests to measure neutron line spectra and hypernuclear γ-quanta. The novel spectroscopy should reveal new information on the structure (deviations from the weak coupling scheme), on the NΛ effective interaction (its possible long-rangedness) and on decay mechanisms.

On the structure of giant dipole resonance in 32S

Abstract The photodisintegration of the 32 S nucleus is calculated in the framework of the microscopical model. The spread of the Fermi surface as well as particle and hole coupling with low-lying states are taken into account. The general features of the calculated absorption spectrum and different photonuclear reactions are discussed. An attempt is made to determine the origin of the peaks in the absorption spectrum on the basis of some reactions and calculated Coulomb form factors. Satisfactory agreement with experimental data is obtained.

Excitation and structure of hypernuclear resonances in (K−,π¯0)-reactions on 1p-shell nuclei

The available experimental data on the excitation functions (EF) of the 1p-shellΛ-hy-pernuclei in (K−, π−) reactions atθπ = 0° has been analysed in terms of shell model and weak coupling scheme. It is substantiated by the experimental data on the neutron spectroscopic factors and on the fragmentation of nuclear hole excitations. The pronounced nuclear spectroscopic characteristics in the hypernuclear spectra are indicative of a weak coupling ofΛ-hyperon with nuclear subsystem. The analysis has made it possible to determine the difference is single-particle energies ofΛ-hyperon in the 1p- and 1s-states and to obtain additional evidence for the smallness of theΛ-nucleus spin-orbit interaction. The resonance structure of EF of hypernuclei, which were not studied in (K−,π0−) reactions, is predicted. The interrelated aspects of the studies of the (K−,π0−), (K−,π0− β′), and (K−, π+) reactions which are of interest to spectroscopy ofΛ-andΣ-hypernuclei are discussed.

The neutron channel in muon capture by 15N and 32S

Abstract The excitation of giant resonances in muon capture by the non-magic nuclei 15 N and 32 S is considered. The capture rates to the levels of the intermediate nuclei 15 C and 32 P as well as neutron decay channels and spectra were calculated. The features of giant resonances in non-magic nuclei are discussed and possibilities of experimentally checking the results obtained are suggested.

Baryonic decay and 1p-shell hypernuclear spectroscopy

The detailed discussion of baryonic decay channels is presented. Levels built on sλp−1, PλP−1 and sλs−1 configurations are considered. The results presented are obtained in the calculations based on the Translationally Invariant Shell Model which automatically includes some intruder states through the kinematic correlations. The role of the intruder states in the proton decay is discussed. The evolution of the baryonic decay width with increasing nucleon number A in the 1p-shell hypernuclei is traced. Hypernuclear decays into the bound excited states either of secondary hypernuclei or nuclei are revealed. Information which could be extracted from the de-excitation of the baryonic decay products whenever they were measured is discussed. From the suggested new set of theλN interaction parameters for the sλp−1 configuration some new information on the proton decay of theΛ12C hypernucleus pλp−1 low-lying levels is given.

Baryon decays and gamma-spectroscopy of hypernuclei

The applicability of (K−,π−γ) - and (K−,π−Nγ)-reactions on13,14C and14,15N nuclei to the study of γ-transitions in primary and daughter Λ-hypernuclei is discussed. The intensity of γ-deexcitation ofΛ13C state |SΛ ⊗12C(15·11 MeV; 1+1): 1/2+〉 has been shown to be comparable with the intensity of baryon decay. Isospin selection rules are used to distinguish excitation energy ranges of primary hypernuclei, where the identification of the secondary γ-lines is probable.

A note on the origin of secondary hypernuclear γ-quanta from Λ 10 B

An alternative interpretation ofΛ10B secondaryγ-quanta due toΛ10B →Λ7Li+3He channel is proposed. Its impact on effectiveΛN interaction properties and on understanding of (s−1sΛ) configurations is discussed and some verifying experiments are put forward.