We present results of shell-model calculations for the proton drip line nucleus ${}^{106}\mathrm{Sb}.$ The shell-model calculations were performed based on an effective interaction for the ${2s1d0g}_{7/2}{0h11}_{11/2}$ shells employing modern models for the nucleon-nucleon interaction. The results are compared with the recently proposed experimental yrast states. A good agreement with experiment is found lending support to the experimental spin assignments.

A study of the role of coupled-channel effects in the enhancement of the population of high-spin states was undertaken with the reactions ${}^{48}\mathrm{Ca}{+}^{142}\mathrm{Nd}$ and ${}^{80}\mathrm{Se}{+}^{110}\mathrm{Pd},$ near the Coulomb barrier, leading to the same compound nucleus, ${}^{190}\mathrm{Hg},$ at the same excitation energy. Statistical calculations with standard values for the level density parameters and fission barriers predict an enhancement of the high-spin population for the more mass-symmetric system, brought about by the coupling to inelastic channels in the fusion process. No enhancement was observed which we interpret as an inadequacy of the fission barriers used, and to the role of the shell corrections, in particular those at the saddle point.

The total cross section for the ${\pi }^{-}\overrightarrow{p}{\pi }^{-}{\pi }^{+}n$ reaction has been measured at incident pion kinetic energies of 200, 190, 184, 180, and 176 MeV, and cross sections for the ${\pi }^{+}\overrightarrow{p}{\pi }^{+}{\pi }^{+}n$ reaction were obtained at 200 and 184 MeV. A fit of these cross sections by heavy baryon chiral perturbation theory yields values of $8.5\pm {0.6(m}_{\pi }^{-3})$ and $2.5\pm {0.1(m}_{\pi }^{-3})$ for the reaction matrix elements ${\mathcal{A}}_{10}$ and ${\mathcal{A}}_{32},$ and, for the s-wave isospin-0 and isospin-2 π-π scattering lengths, the values $a_0=0.23\mathrm{}\pm {0.08(m}_{\pi }^{-1})$ and $a_2=-0.031\pm {0.008(m}_{\pi }^{-1}),$ respectively.

In terms of the interacting boson model (IBM), shape invariants for the ground state, formed by quadrupole moments up to sixth order, are studied in the dynamical symmetry limits and over the whole structural range of the IBM-1. The results are related to the effective deformation parameters and their fluctuations in the geometrical model. New signatures that can distinguish vibrator and γ-soft rotor structures, and one that is related to shape coexistence, are identified.

Deformation and orientation effects on compression, elliptic flow, and particle production in uranium on uranium collisions (UU) at relativistic energies are studied within the transport model ART. The density compression in tip-tip UU collisions is found to be about 30% higher and lasts approximately 50% longer than in body-body or spherical UU reactions. The body-body UU collisions have the unique feature that the nucleon elliptic flow is the highest in the most central collisions and remains a constant throughout the reaction. We point out that the tip-tip UU collisions are more probable to create the quark gluon plasma (QGP) at Alternating Gradient Synchrotron and Super Proton Synchrotron energies, while the body-body UU collisions are more useful for studying properties of the QGP at higher energies.

One-loop corrections at the two-nucleon level to pion double charge exchange scattering off a nuclear target at threshold are calculated within the framework of heavy baryon chiral perturbation theory. An estimate for the (two-nucleon) one-loop correction is obtained in the static limit and using an impulse approximation. We find a small (1.6%) increase relative to the leading order tree graphs.

We use the empirical evidence that F-spin multiplets exist in nuclei for only selected states as an indication that F spin can be regarded as a partial symmetry. We show that there is a class of non-$F$-scalar IBM-2 Hamiltonians with partial F-spin symmetry, which reproduce the known systematics of collective bands in nuclei. These Hamiltonians predict that the scissors states have good F-spin and form F-spin multiplets, which is supported by the existing data.

The relationship between pion and kaon space-time freeze-out distributions and the Hanbury Brown–Twiss (HBT) radius parameters in high-energy nucleus-nucleus collisions is investigated. We show that the HBT radius parameters in general do not reflect the rms deviations of the single particle production points. Instead, the HBT radius parameters are most closely related to the curvature of the two-particle space-time relative position distribution at the origin. We support our arguments by studies with a dynamical model (RQMD 2.4).

Measurement of the energy of neutrons in coincidence with the production of free ${\Xi }^{-}$ hyperons can be used to determine the masses of ${}_{\Lambda \Lambda }^{12}\mathrm{B}$ hypernuclear states and branching ratios of their formation from $({\Xi }^{-}{,}^{12}\mathrm{C}{\overrightarrow{{)}_{\mathrm{atom}}}}_{\Lambda \Lambda }^{12}\mathrm{B}+n.\mathrm{}$ The E885 Collaboration utilized the Alternating Gradient Synchrotron $1.8\hspace{0.5em}\mathrm{GeV}/c\hspace{0.5em}{K}^{-}$ beam incident on a diamond target to accumulate the largest-to-date data sample of ${(K}^{-}{,K}^{+})$ events. A total of about $3\times {10}^5\hspace{0.5em}{(K}^{-}{,K}^{+})$ events have been collected and analyzed. The neutron spectrum shows no apparent peaks from the neutron-emission channel of double-$\Lambda$ hypernuclear formation from $({\Xi }^{-}{,}^{12}\mathrm{C}{)}_{\mathrm{atom}}$ decay. The upper limit on the branching ratio of the above process has been set to be at or below 4% in the region of expected neutron energies.

Recent results for pion absorption on ${}^{12}\mathrm{C}$ by the CHAOS group at TRIUMF have brought into question much of the understanding of pion absorption on light nuclei. We performed a critical evaluation of the CHAOS results and a detailed comparison to other specific experiments. We conclude that limitations in the CHAOS analysis are primarily responsible for the disagreements with the established picture of pion absorption.

The strength functions of the hot giant dipole resonance (GDR) in ${}^{120}\mathrm{Sn}$ obtained within the phonon damping model (PDM) have been included in the complete statistical calculations and compared with their experimental divided spectra as a function of temperature T. The entire experimental shape of the hot GDR can be reproduced reasonably well using the PDM strength functions. The effect of superfluid pairing at $T<\mathrm{}1\mathrm{}$ MeV is important to obtain a better agreement between theory and data.

A description of $\alpha$-like resonances is given in terms of single-particle states including narrow Gamow resonances in continuum. The equations of motion are derived within the multistep shell-model approach; the lowest collective two-particle eigenmodes are used as building blocks for the four-particle states. A good agreement with the low-lying states in ${}^{212}\mathrm{Po}$ is obtained. A new technique to estimate the $\alpha$-particle formation amplitude for any multipolarity is proposed. The spectroscopic factor of the $\alpha$-decay between ground states is reproduced, but the total width is by two orders of magnitude less than the experimental total width, due to the absence of the background components. The $\alpha$-like structure of the lowest states in ${}^{212}\mathrm{Po}$ is analyzed and strong high-lying resonances are predicted. The derived equivalent local potential for the $\alpha$-particle scattering has a molecular shape.

Supersymmetric transformations, i.e., factorizations of the radial Schrödinger equation, are generalized to potentials with a linear dependence on energy. These transformations are equivalent to generalized Darboux transformations and do not affect the energy dependence of the potential. A pair of transformations allows the removal of a bound state without modification of the phase shift. The method is applied to the removal of the forbidden bound states of a deep energy-dependent $\alpha {+}^{16}\mathrm{O}$ potential generating a phase-equivalent shallow potential with an $r^{-2}$ repulsive core at the origin and the same energy dependence as the initial potential.

The scattering cross sections of charm mesons with hadrons such as the pion, rho meson, and nucleon are studied in an effective Lagrangian. In heavy ion collisions, rescattering of produced charm mesons by hadrons affects the invariant mass spectra of both charm meson pairs and dileptons resulting from their decays. These effects are estimated for heavy ion collisions at Super Proton Synchrotron energies and are found to be significant.

Correlation functions for $p-p,$ $p-d,$ $p-\alpha ,$ $d-\alpha ,$ and $\alpha -\alpha$ were measured for the ${}^{16}\mathrm{O}{+}^{27}\mathrm{Al}$ system at a beam energy of 72 MeV. The detector array was centered at laboratory angle of $20°.$ Compared to published data obtained at larger scattering angles, an unexpected dependence on angle is seen for the $p-p$ channel. The observed anticorrelation is stronger at more forward angles, which suggests that correlation functions are sensitive to the specific reaction mechanisms producing the light-charged particles.

The photodisintegration of deuterium with linearly polarized light has been measured in the energy range of 110–315 MeV. The results of five independent measurements using three detector systems, two liquid target geometries, and two photon energy distribution end points are presented. These data are combined into one average data set with a systematic uncertainty of ±5%. The statistical precision of this combined data set, coupled with the sensitivity to the strength of the short range tensor interaction observed in the parallel-perpendicular cross section difference, makes this an attractive reaction for investigating aspects of the NN interaction. To do this reliably requires a complete, systematic description of the reaction through the Δ region. Recent $NN-N\Delta$ coupled-channel calculations which include fully retarded pion potentials are compared with multipole fits to the data. These calculations cannot reproduce the energy and angle dependence of the data. The character of the disagreement suggests that the remaining problems may lie with the treatment of the Δ.

We study the effects of friction on the chiral symmetry restoration which may take place temporarily in high energy heavy ion collisions. The equations of motion with friction are introduced to describe the time evolution of the chiral condensates within the framework of the linear $\sigma$ model. Four types of friction are used to study how the result is sensitive to the choice of the friction. For the thermalization stage, the time dependent temperature is parametrized so as to simulate the result of the parton-cascade model. It is parametrized according to the one-dimensional scaling hydrodynamics for the subsequent cooling stage. The time development of the condensates and the entropy production due to friction are calculated numerically. The time interval in which the chiral symmetry is restored approximately is investigated in detail for four types of friction. It is found that (i) the maximum temperature must be high enough (not lower than 230 MeV) and the friction must be strong enough in order that the chiral symmetry restoration lasts for a long time (not shorter than 3fm/c), (ii) the ratio of time interval in which chiral symmetry is restored, to the time interval in which the temperature is higher than the critical temperature is typically 0.5 when the friction is strong enough, and (iii) the entropy due to the friction is mainly produced in the early stage of the cooling. The effect of freeze-out is discussed briefly.

The E2-transition probabilities are calculated for high-spin states in the ytterbium isotopes ${}^{160,164,168}\mathrm{Yb}$ by projecting out exact angular momentum states from cranked Hartree-Fock-Bogoliubov (CHFB) intrinsic wave functions. It is shown that the projected CHFB theory describes reasonably well the overall trend of the experimental $B\left(E2\mathrm{}\right)\mathrm{}$ values along with spin, exhibiting their substantial reduction in the band-crossing region.

To understand the various results on the $N^{*}\left(1440\mathrm{}\mathrm{M}\mathrm{e}\mathrm{V}\right)$ resonance in a consistent way, the data on $\alpha -p$ scattering at $E_{\alpha }=4.2\mathrm{}\mathrm{GeV}$ were reanalyzed assuming projectile and target excitation, and their interference. A quantitative fit of the spectrum is obtained, assuming for the $N^{*}$ mass distribution a threshold modified Breit-Wigner shape with momentum-dependent width and resonance parameters $M=1390\mathrm{}\pm 20\mathrm{MeV}$ and $\Gamma =190\mathrm{}\pm 30\mathrm{MeV}.$ This, however, is not consistent with the data on π-N scattering which, in general, require a higher resonance mass and a larger width. Both systems, α-p and π-N, can be described consistently in a T-matrix formalism, assuming two structures in the $P_{11}\left(1440\mathrm{}\mathrm{MeV}\right)$ resonance, from which only the first one is observed in α-p. For this structure the elastic π-N width is small and the decay into the $2\pi \mathrm{}\left(s\right)-N$ channel is large. This strongly supports the conclusions drawn from α-p scattering. The second structure at higher mass has a strong decay into the πΔ channel and can be well understood as a second-order excitation of the $\Delta \left(1230\mathrm{}\mathrm{MeV}\right).\mathrm{}$ The two resonance picture of the $P_{11}\left(1440\mathrm{}\mathrm{MeV}\right)$ resonance is supported by γ-induced reactions; no evidence is found for the first $N^{*},$ however, the second resonance is observed (although more or less obscured by nonresonant π-Δ production). A further crucial test of the existence of two structures in the Roper resonance is provided by exclusive α-p experiments; a $N^{*}$ decay pattern should be found quite different from π-N with a very strong 2π decay.

We study the structure of He isotopes systematically using a model in which the frameworks of the antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM) are combined. The present AMD+GCM can reproduce basic features of the isotopes, for example halo structures in ${}^6\mathrm{He}$ and tendency of the binding energies of the isotopes within relatively small number of basis functions. In ${}^7\mathrm{He},$ the importance of two configurations, ${}^6\mathrm{He}-n$ and ${(}^4\mathrm{He}-n)–2n,$ is shown for the ground state. In ${}^8\mathrm{He},$ the calculated rms radius is smaller than the experimental one.