The asymmetries $A_{\mathrm{NN}}$ and $A_{\mathrm{LL}}$ have been measured at small angles for the p→ p→→d${\pi }^{+}$ reaction at 650 and 800 MeV. Now complete angular distributions are integrated to obtain the contribution of this channel to Δ${\sigma }_L$. These contributions are combined with those from the elastic channel to determine Δ${\sigma }_L$(p→ p→→NNπ) at 650 (=0.775±0.5 mb) and 800 (=-1.52±0.6 mb) MeV. There is pronounced disagreement between these data and the predictions of conventional theories. $A_{\mathrm{NN}}$ and $A_{\mathrm{LL}}$ also compared with theoretical predictions and their influence on partial-wave analyses is discussed.

The pion-proton bremsstrahlung process is considered in a Δ-isobar model that treats the full Lorentz structure and off-shell nature of the Rarita-Schwinger spin-(3/2 propagator and vertex functions. The relativistic isobar model necessarily produces background $S_{31}$, $P_{31}$, and $D_{33}$ partial waves as well as the resonant $P_{33}$ wave, but explicit background is needed to fit the elastic data. Unitarity and gauge invariance as well as the soft photon limit are preserved in the model. The ${\pi }^{+}$-p elastic and radiative processes are treated on the same dynamical footing within a relativistic K-matrix approach. The approach is constructed in a form that formally resembles a four-dimensional scattering theory to allow a more physical or intuitive illustration of the underlying dynamics.

A simple quark model is used to define a nuclear pair model, that is, two composite hadrons interacting only through quark interchange and bound in an overall potential. An equivalent hadron model is developed, displaying an effective hadron-hadron interaction which is strongly repulsive. We compare the effective hadron model results with the exact quark model observables in the kinematic region of large momentum transfer, small energy transfer. The nucleon response function in this y-scaling region is, within the traditional framework, sensitive to the nucleon momentum distribution at large momentum. We find a surprisingly small effect of hadron substructure. Furthermore, we find in our model that a simple parametrization of modified hadron size in the bound state, motivated by the bound quark momentum distribution, is not a useful way to correlate different observables.

It is shown that the oscillator spacing ħ${\omega }_{\Lambda }$ in hypernuclei may be given by an approximate closed-form analytic expression containing the dependence on the mass number of the core nucleus A to all orders of $A^{\mathrm{-}1/3}$. This expression, or preferably its leading terms $c_1$$A^{\mathrm{-}1/3}$-$c_2$$A^{\mathrm{-}2/3}$, can be used to estimate the lowest Λ-excitation spacing. The region of its validity is discussed. The variation with A of the ground state kinetic and potential energy of the Λ and its rms radius are also examined.

The estimation of the relativistic Coulomb wave function is a time-consuming procedure, when the experimental data on the double beta decays are analyzed or the Monte Carlo calculation is performed. In order to avoid this complication, some simple approximated formulas are derived for three modes: the double beta decay with two neutrino emission, the neutrinoless double beta decay, and the neutrinoless double beta decay with Majoron emission. The errors of these approximations are of order of 1% or less in the region where decay events are measured practically.

Available experimental data on neutron decay spectra from the E1 giant resonances in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ are compared with the predicted spectra for statistical decay. The calculations are performed using the Hauser-Feshbach formalism with the experimental levels of the residual nuclei. The particle-vibrator model is used to assign spins and parities to experimental levels when those are unknown and also to predict the levels where there is not enough experimental information.

The interacting boson-fermion model is used to analyze beta decay. The beta transition operator in the boson-fermion space is constructed with the parameters obtained from microscopic considerations. The ft values are calculated for the first nonunique forbidden transitions between states based on natural parity orbitals in the decays of ${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{195}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$. The structure of the odd-neutron nuclei is described in the U(6)⊗U(12) boson-fermion symmetry limit. For the odd-proton nuclei, three different approaches, in particular the U(6)⊗U(4) symmetry, the U(6)⊗U(20) symmetry, and the perturbed U(6)⊗U(4) scheme, are compared. The calculated ft values are very sensitive to details of nuclear wave functions, the best results being obtained with the perturbed U(6)⊗U(4) scheme. Phase ambiguities in nuclear wave functions can be disentangled from beta decay analysis. The exchange terms in the boson-fermion transition operator, which take into account the Pauli principle between the odd-nucleon and nucleons forming the even-even collective core, proved to be quite important.

The numerical values of $g_A$ are evaluated using quantum-chromodynamic sum rules. The nuclear medium effects are taken into account by modifying the chiral symmetry breaking correlation, 〈q¯q〉. Our results indicate a quenching of $g_A$ in a nuclear medium. The physical reasons for this fundamental quenching are noted to be the same for the effective mass of the nucleon bound in a nucleus being less than its free space value.

A single high resolution intrinsic Ge detector was used to measure the gamma–K-x-ray sum coincidences in the electron capture decay of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Ba}$. The sum spectrum was then analyzed in order to determine the relative K-capture probabilities to different levels in ${}_{}{}^{131}{}_{}{}^{}\mathrm{Cs}$. The measured $P_K$ ratios compare well with the theoretical results.

We study the dynamic symmetries in deformed odd-even nuclei and show the correspondence with a description in terms of the Nilsson model and the semi-microscopic interacting boson-fermion approximation model.

The theory of large amplitude adiabatic motion is applied to a recently proposed model of tunneling in many body systems. We construct the corresponding collective Hamiltonian and study the applicability of the decoupling procedure, both by comparing the results of the large amplitude theory with exact results and by studying different measures of the decoupling procedure, including the stability of the collective motion against noncollective vibrations. We also analyze briefly another approximation scheme especially suited for the problem at hand. The theory of large amplitude collective motion provides an extremely accurate description of the collective motion and of the tunneling process.

Statistical shape fluctuations are calculated for ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ at spins 0 and 40ħ. The fluctuations produce an average shape, which is distinct from the most probable (i.e., mean field) shape. At low temperatures the average shape is similar to the most probable shape, and the shape fluctuations are small. With increasing temperature the shape fluctuations increase, as does the difference between the average shape and the most probable shape. The fluctuations smooth out the sharp shape transitions predicted by mean field theories. Although the most probable phase at spin 40ħ and critical temperature 1.64 MeV is oblate noncollective rotation, the fluctuations create a high probability for prolate collective, prolate noncollective, and oblate collective rotations as well.

A survey of observed E0 transition strength shows that some of the largest strength occurs for transitional nuclei whenever large mixing between almost spherical and largely deformed shapes results. This leads to the conclusion that large E0 strength is not an indication of coexisting shapes but of strong mixing between nuclear states with largely different radii. In addition, we discuss the variation of E0 transition rates in regions where intruder states become the nuclear ground state. We illustrate this by recent results in the A≃100 region concentrating especially on the anomalously large monopoles strength and its variation in the even-even N=60 isotones as compared with the N=58 isotones.

For an even number of nucleons, we consider collective motion based on any dynamical symmetry subalgebra  of the valence-shell bifermion algebra; the generators of  are coherent linear combinations of bifermion operators of the types $a^{\mathrm{°}}$$a^{\mathrm{°}}$, $a^{\mathrm{°}}$a, and aa. A boson algebra is obtained by Dyson mapping the whole valence-shell bifermion algebra, and then ‘‘skeletonizing’’ the resulting expressions by deleting all noncollective boson operators from them. This skeleton boson algebra is shown to have the same commutation relations as the collective bifermion algebra, provided that the bifermion algebra is self-conjugate. The resulting boson Hamiltonian is not Hermitian, but does resemble the Hamiltonian of the interacting boson model in containing only one- and two-body terms. Moreover, the skeleton boson algebra (when restricted to a collective boson subspace that is free of spurious states) is shown to be physically equivalent to the collective bifermion algebra. It is shown that by working solely with collective bosons one can identify spurious boson states unambiguously, although the procedure lacks convenience. The similarity transformation that connects conjugate versions of the skeleton boson mapping is discussed, and a general condition for hermiticity of the boson image of a Hermitian operator is given.

A recent analysis of the correspondence between fermion and boson spaces is extended to systems with an odd number of fermions. A fermion space is now mapped onto a boson-fermion space. The case is discussed of the SD-j and sd-j spaces, i.e., spaces in which an odd particle moving in a j orbit is coupled to systems of S,D pairs and s,d bosons, respectively. The sd-j image of the quadrupole-quadrupole interaction is constructed both for systems of identical particles and for proton-neutron systems. Numerical comparisons are shown between spectra in the SD-j and sd-j spaces. The role of the exchange term in the sd-j Hamiltonian is analyzed. The comparison with other mapping techniques as well as with phenomenological Hamiltonians is discussed.

We apply the t-expansion method of Horn and Weinstein to the SU(2) soluble model of Lipkin. The method is shown to approximate well both the ground state and the first excited state energies. An extension to a dynamically determined reference state is explored and shown to dramatically improve results for the region of strong coupling.

Applications of a procedure recently proposed to construct boson images of fermion Hamiltonians are shown for proton-neutron systems. First the mapping from SD fermion onto sd boson spaces is discussed and a $Q_{\pi }$⋅$Q_{\nu }$ interaction investigated. A Hermitian one-body Q boson operator is derived and analytical expressions for its coefficients are obtained. A ($Q_{\pi }$+$Q_{\nu }$)⋅($Q_{\pi }$+$Q_{\nu }$) interaction is, then, studied for particle-hole systems and the connections with the ${\mathrm{SU}}^{\mathrm{*}}$(3) dynamical symmetry of the neutron-proton interacting boson model are discussed. Finally, an example of mapping from SDG onto sdg spaces is analyzed. Fermion spectra and E2 matrix elements are well reproduced in the boson spaces.

We discuss a new parity-violating mechanism specific for nucleons bound in the nucleus. The mechanism consists of weak emissions and absorptions of mesons by a single nucleon in the presence of the strong nuclear field, and generates a parity-violating correction to the nuclear potential. The contribution of the low-mass mesons π, ρ, and ω to the new potential is completely evaluated.

A search has been conducted for the exotic neutron rich nucleus ${}_{}{}^{10}{}_{}{}^{}\mathrm{He}$ among projectile fragments produced by an E/A=30 MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ beam. No ${}_{}{}^{10}{}_{}{}^{}\mathrm{He}_{}^{2+}{}_{}{}^{}$ ions were observed. The upper limit on the production rate of ${}_{}{}^{10}{}_{}{}^{}\mathrm{He}$ is determined to be less than 3×${10}^{\mathrm{-}5}$ that of ${}_{}{}^8{}_{}{}^{}\mathrm{He}$.

We have measured the transverse and the longitudinal polarization transfer coefficients $K_y^{y\mathcal{’}}$ and $K_z^{z\mathcal{’}}$ at 0° in the (p,n) reactions from ${}_{}{}^6{}_{}{}^{}$,7Li and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ for proton energies near 55 MeV. Except for the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(p,n)Be reaction, where $K_y^{y\mathcal{’}}$(0°)=-0.33±0.04, all transfer coefficients are <0.20 and thus not very suitable for the production of polarized neutrons.