Exchange magnetic moments of some odd-mass nuclei

The exchange magnetic moment has been calculated for the nuclei ⁹¹Zr, ⁸⁹Sr and ⁸⁷Kr in the ground state. By adding the core polarization contribution to the magnetic moments computed earlier, an improved value is obtained for the magnetic moments of these nuclei.     

Radiative muon capture for N = Z nuclei

The commonly used elementary hamiltonian of radiative muon capture has been confirmed, while the alternative Hwang-Primakoff approach is shown not to be gauge invariant.In the inclusive process on N = Z nuclei, the closure approximation is avoided by using a realistic nuclear excitation spectrum.The study is exemplified by a detailed application to ⁴⁰Ca. Predictions are given for the high-energy photon spectrum, circular polarization and asymmetry with respect to the muon polarization for various values of the pseudoscalar coupling constant g_p. A semi-quantitative agreement is found with the data on the spectrum; more precise experiments are necessary to determine g_p.     

Proton-neutron correlations in nuclei with N = 30

Structure of the nuclei with N = 30 and Z = 20–28 is investigated by the nuclear shell model within the proton-neutron configurations (1f_{$\text{7}\text{2}$})^z?20_p × (2p_{$\text{3}\text{2}$}, 2p_{$\text{case1}\text{2}$}, 1f_{$\text{case5}\text{2}$})²_n. Effective proton-neutron interactions determined by a least-squares fit to the observed spectra of N = 29 nuclei are adopted. Agreement of the calculated spectra with experimental spectra is satisfactory. Strong correlations between protons and neutrons break down the pairing scheme and lower the first J = 2 levels in doubly even nuclei, which is shown from the resultant wave functions. A relation between the shell model and collective rotational model is discussed concerning the calculated rotation-like spectrum of ⁵⁶Fe. Electromagnetic properties and spectroscopic factors of single-nucleon transfer reactions are calculated. They are in good agreement with experiments.     

N = 1 superspace formulation of N = 2 and N = 4 super-Yang-Mills models with central charge

The component models of N = 2 and N = 4 supersymmetric Yang-Mills theories of Sohnius, Stelle and West are reformulated in terms of N = 1 superfields. The non-supersymmetric constraints are supersymmetrized generalizing the linear multiplet in the presence of the non-abelian gauge superfield and (in the N = 4 case) a doublet of chiral superfields. The extended supersymmetry transformations preserving constraints are explicitly given in terms of N = 1 superfields. We are able to introduce the constraints back into the lagrangian using superfield Lagrange multipliers. The on-shell equivalence of this formulation with the formulation of Fayet with one (for N = 2) and three (for N = 4) chiral superfields is shown. The abelian N = 2 model is worked out to show the connection between full superspace treatment and the N = 1 superfield formulation.     

Iinelastic electron scattering calculations on N = 50 isotones

The first excited 2⁺, 3^? and 4⁺ levels in ⁸⁸Sr, ⁹⁰Zr and ⁹²Mo are described by the seniority υ = 2 shell model and by the two-quasiparticle BCS model. In both models the DWBA cross sections for inelastic electron scattering are calculated. It appears that both models often give the same cross sections, the overall normalisation being then the difference. The agreement with the experimental data for ⁹⁰Zr and ⁹²Mo for the shell model case is much better than for the BCS model.     

N = 2 supergravity action in terms of N = 1 superfields

We construct the full N = 2 supergravity action in terms of N = 1 supergravity and matter fields.     

Beta decay log ft values for transitional odd-mass nuclei

Using the wave functions yielded by the asymmetric rotor model with a decoupled odd nucléon with variable moment of inertia the absolute log ft values for some transitional odd-mass nuclei have been calculated. The dependence on the γ-deformation is important in a few cases. A great improvement is obtained in comparison with a pure spherical shell-model calculation.     

N = 4 supergravity coupled to N = 4 matter and hidden symmetries

We present the N = 1 supergravity in 10 dimensions obtained by truncating the reduced N = 1 supergravity from 11 dimensions. This is further reduced to 4 dimensions to give SU(4) supergravity coupled to six SO(4) vector multiplets. As the reduction is from 10 dimensions, the theory is expected to have the symmetry SL(6R)_global×SO(6)_local, but we give a theoretical argument that this can be extended to SO(6,6)×SU(1,1)_global and SO(6)×SO(6)×U(1)_local.     

N = 8 supergravity

The complete structure of N = 8 supergravity is presented with an optional local SO(8) invariance. The SO(8) gauge interactions break E₇ invariance, but leave the local SU(8) unaffected. Exploiting E₇ × SU(8) invariance and using explicit lowest order results, we first derive the complete action and transformation laws. Subsequently, we introduce local SO(8) invariance and prove the consistency of the theory. Possible implications of our results are discussed.     

N = 4 Yang-Mills theory in terms of N = 3 and N = 2 light-cone superfields

The N = 4 Yang-Mills theory is truncated to an N = 3 Yang-Mills theory and to an N = 2 Yang-Mills theory coupled to an N = 2 Wess-Zumino field. The whole procedure is performed in the light-cone gauge. It is then shown that these theories are unique even if we only insist on N = 3 or N = 2 supersymmetry respectively. Finally we show in detail how the introduction of the fermionic Wess-Zumino field renders the one-loop self-energy finite.     

Rotational description of the negative-parity states in transitional N = 89 nuclei

It is demonstrated that level energies and pick-up spectroscopic factors for the low-spin negative-parity states in transitional N = 89 nuclei can be successfully described in the particle-rotor model with Nilsson single-particle orbitals, provided that both Coriolis and recoil effects are properly taken into account.     

Bound states in N = 8 supergravity and N = 4 supersymmetric Yang-Mills theories

We present a study of possible bound states in N = 8 supergravity. We find evidence for the existence of multiplets of two-body bound states and expect that many-body bound states may exist as well. Our study is based on a calculation of Regge trajectories in the two-body scattering amplitudes of the lagrangian field theory. We also study Regge trajectories in N = 4 Yang-Mills theory and find evidence for a possible spin zero, SU(4) and gauge singlet, massless bound state. If such a state actually exists and supersymmetry is not broken, it may be a member of a supersymmetric multiplet which includes the graviton.     

(γ, p) cross sections and isospin splitting of the giant dipole resonance in N = 50 nuclei

The differential (e, e'p) cross sections of ⁸⁸Sr, ⁸⁹Y, ⁹⁰Zr and ⁹²Mo have been measured at θ = 90°. The results are used to obtain the (γ, p) cross sections by correcting with the angular distribution data. The (γ, p) cross sections are compared with the (γ, n) cross sections. A resonance corresponding to the T_< GDR is found and another resonance is separated by fitting a Lorentz line with a width equal to that of the (γ, n) GDR. The ratios σ(γ, p)/σ(γ, n) and σ(γ, p₀)/σ(γ, p) show differences between the two resonances. The two GDR resonances are studied from the isospin splitting point of view. The sum rule and splitting energy of the (γ, p) GDR agree well with theory. However, when the sum of the (γ, p) and (γ, n) experimental data is taken, the results are too large to be explained by the T_> GDR.     

Total muon capture rates for N = Z nuclei in the 1p shell

The approach to total muon capture rates by means of sum rule techniques is applied systematically to 1p shell nuclei. Explicit calculations involve ground-state wave functions extracted from Cohen-Kurath effective interactions. For the double commutator expectation value we use a form of the potential consistent with the effective interaction and the giant dipole resonance energy.Results are given for N = Z nuclei, studying the minimal sensitivity with the parameter of the improved closure approach. The manifestations of SU(4) breaking are quantitatively shown. Within the uncertainties of the model the rates thus obtained compare reasonably well with experiment.     

Shell-model study on magnetic dipole excitation of N = 28 isotones

Magnetic dipole excitation of N = 28 isotones — ⁴⁸Ca, ⁵⁰Ti, ⁵²Cr, ⁵⁴Fe and ⁵¹V — is studied in terms of the shell model by assuming $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{n?m}}\text{(}\text{p}\text{3}\text{2}\text{p}\text{1}\text{2}\text{f}\text{5}\text{2}\text{)}{}^{\mathrm{m}}$ configurations with m = 0, 1 and 2 on an inert ⁴⁰Ca core. Strength distributions observed in (e,e′) and (p,p′) experiments are fairly well reproduced. Interference of proton and neutron excitations enhances B(M1) values around E_x = 10 MeV and reduces those of low-lying states. The strength for T = T₀ + 1 states substantially increases when orbital magnetization is not taken into account, whereas no appreciable consequences can be seen for T = T₀ states. In comparison with single-particle model predictions with m = 0, about 20–30% reduction of the total strength is obtained due to ground-state configuration mixing. It is shown that the isoscalar spin component is reduced as well as the isovector one. However, the theoretical total strength is still much larger than experimental values, and coupling with high-lying configurations and possible delta-hole excitation might be required in order to account for the discrepancy. In an odd-mass nucleus ⁵¹V, the ground-state transition strength is distributed continuously over a wide energy range, being very strongly fragmented.     

Noncompact N=2 supergravity

A massive spin-one multiplet with central charge is coupled to N=2 supergravity. Compared to conventional gauge fields the anomalous magnetic moment of the spin-one particles is of the opposite sign. The construction of this theory is based on an N=2 supersymmetric gauge theory associated with the noncompact group SO(2,1). As a byproduct we present a convenient expression for the N=2 Einstein-Yang-Mills lagrangian.     

The complete N =2, d = 10 supergravity

The alternative N = 2, d = 10 supergravity, which is not derivable by dimensional reduction from the N = 1, d = 11 theory, is constructed at the full non-linear level. The transformation laws of the component fields and the equations of motion are derived and shown to be consistent. The derivation makes use of superspace techniques and exploits the fact that the scalars belong to the coset space SU(1,1)/U(1).     

The systematics of nuclear single-particle states of nuclei with 50 ≦ NZ ≦ 82

The depth of the local Woods-Saxon potential corresponding to the experimental binding energies of the single particle states in gdhs nuclei has been parametrized as a function of the mass number A and the symmetry parameter (N?Z)/A. A typical spread of 200 keV of the calculated values of the potentials from the best fit curve was obtained. The implication of the pairing correlations are discussed.     

Unambiguous identification and properties of high spin isomers in nuclei close to N = 82

The search for and study of high spin isomers produced by ¹²C, ¹⁴N and ¹⁶O induced reactions on targets close to N = 82 has been performed. The observed isomers were identified unambiguously by a detailed study of the excitation functions, delayed gamma-ray multiplicity and multiparametric gamma-gamma coincidences. The isomers with the highest spin above the ground state were observed in ¹⁵²Er and ¹⁵¹Ho nuclei.