R.A. Eramzhyan

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.

Towards a better understanding of 16O nuclear structure: Muon capture and radiative pion capture reactions

Abstract Muon capture and radiative pion capture reactions on 16 O have been analysed with the aim to extract more information on the importance of higher components of the A = 16 nuclear ground and excited states. Good agreement with the experimental data for both reactions may be achieved if at least 2p2h components of the nuclear wave functions are taken into account. The positive parity excited states in 16 N are shown to contribute 43 % to the radiative π − capture but only ≈ 10 % to the muon capture rate.

Partial transitions in radiative pion capture on light atomic nuclei

Abstract The partial transitions in radiative pion capture on light nuclei are studied within the shell model with intermediate coupling. The probabilities of capture from s- and p-states of a mesoatom and the total yield of γ-quanta have been calculated and compared with experimental data.

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.

Decay properties of hypernuclear resonances

Abstract Analysis of baryon decay channels of (p −1 N , s Λ ) resonances above thresholds as produced in (K, π) reactions is presented for hypernuclei from Λ 7 Li to Λ 16 O. The possibilities of Λ-hypernuclear spectroscopy are reviewed. Baryon decay line spectra and hypernuclear γ-quanta (both soft and hard) would reveal substantial information on hypernuclear structure, ΛN interaction and nature of small resonance widths.

Pion photoproduction and inelastic scattering in A=12 nuclei: Transitions to the lowest isovector 1+ and 2+ levels

Abstract The continuity equation for the nuclear electric charge and convection current ▿ · j N = −α ρ N ρt has been used in an analysis of nuclear transition densities in 12 C. The results differ considerably from the former derivations. The standard M1 and newly-calculated E2 nuclear structure input is applied to estimate the pionic cross sections. A consistent improvement in several instances over the earlier results has been achieved; the calculations agree nicely with data both in the (3, 3) resonance region and at lower pion energies.

Spin dipole excitations in radiative pion capture on 1p shell nuclei

Abstract Shell-model calculations for spin-dipole transitions in the ( π − , γ ) reaction on 6,7 Li, 9 Be, 11 B, 13 C and 14 N are compared with experimental data. The gross structure of resonance is discussed in terms of configurational splitting and symmetry considerations. Quantum numbers of resonances, total and partial yields are considered. Selected ( π − , γ n) and ( gp − , γ n γ ′) coincidence experiments are proposed. The role of quadrupole and quasielastic excitation is also briefly 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.

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.

Collective resonances with isospin T = 2, 1 and 0 in photoreactions, low-q electron scattering and radiative pion capture on A = 14 nuclei

Abstract Shell model predictions are given for: (a) photoreactions, (b) low- q electroexcitation at backward angles, and (c) radiative pion capture on A = 14 nuclei. The experimental evidence on T = 2 resonances in reactions (a) and (b) is discussed. All three types of reactions on 14 C are considered as promising for locating collective states with unusual isospin.