Measured values of the differential cross section for pion-nucleon charge exchange, ${\pi }^{-}p\to {\pi }^{0}n$, are presented at ${\pi }^{-}$ momenta of 148, 174, 188, 212, 238, 271, 298, and $323\mathrm{MeV}∕c$, a region dominated by the $\Delta \left(1232\right)$ resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically $2–6\%$, exceptions being the results at the lowest momentum and at the most forward measurements at the five lowest momenta. We estimate the systematic uncertainties to be $3–6\%$.

A detailed examination of all the available $\log ft$ values for $\beta$ transitions in heavy $\left(A>228\right)\text{nuclei}$ reveals a very similar distribution of these values for the allowed and the first-forbidden decays in this region, in sharp contrast with the observed trends over the whole periodic table. Data for over 500 transitions belonging to both the allowed and forbidden categories are presented in the form of histograms. Physical basis for this unusual behavior is sought by examining the interrelationships between the Nilsson model asymptotic quantum numbers of the $\beta$ connected states. Explicit selection rules specific to this region, in terms of these quantum numbers, are proposed and their applicability is demonstrated by citing illustrative examples from the allowed decays of odd-$A$ actinides.

Using many-body perturbation theory and coupled-cluster theory, we calculate the ground-state energy of ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$. We perform these calculations using a no-core $G$-matrix interaction derived from a realistic nucleon-nucleon potential. Our calculations employ up to two-particle two-hole coupled-cluster amplitudes.

A photon scattering experiment with bremsstrahlung has been performed on the vibrational nucleus ${}^{142}\mathrm{Ce}$ up to a photon endpoint energy of $4.1\text{MeV}$. Fourteen dipole excitations have been observed between 2.1 and $3.9\text{MeV}$, five of them for the first time. A candidate for the $1^{-}$ dipole member of the recently proposed quintuplet of negative parity ${\left(2_{1,\text{ms}}^{+}\otimes 3_1^{-}\right)}^{\left(J^{-}\right)}$, involving the $2_{1,\text{ms}}^{+}$ isovector quadrupole excitation in the valence shell, has been identified. This exotic $1_{\text{ms}}^{-}$ state has been predicted within the $sdf$-IBM-2 and is expected to be accessible to photon scattering measurements. Solely one of nine $J=1$ states in the energy region of interest shows a decay pattern compatible with the model predictions for the $1_{\text{ms}}^{-}$ state.

We study the nuclear medium effects on the $c\bar{c}$ time evolution and charmonium production in a relativistic proton-nucleus collision. Little is known of the nuclear effects in the fragmentation region where the charmonium formation length is shorter than the nuclear size. We use a quantum-mechanical model which includes an imaginary potential to describe the $c\bar{c}$-nucleon collisions. This introduces a transition amplitude among the charmonium states and results in an interference pattern in the survival probability, and is particularly pronounced for ${\psi }^{\prime }$. We present the comparison with data from NA50 and E866∕NuSea and make predictions for the $J∕\psi ,$ ${\psi }^{\prime }$, and ${\chi }_c$ suppression factors as a function of the nuclear mass, and for the negative $x_F$ region, where data will be available soon.

${}^{13}\mathrm{N}\left(p,\gamma \right){}^{14}\mathrm{O}$ is one of the key reactions which trigger the onset of the hot CNO cycle. This transition occurs when the proton capture rate on ${}^{13}\mathrm{N}$ is faster, due to increasing stellar temperature $\left(⩾{10}^8\mathrm{K}\right)$, than the ${}^{13}\mathrm{N}$ $\beta$-decay rate. The rate of this reaction is dominated by the resonant capture through the first excited state of ${}^{14}\mathrm{O}$ $\left(E_r=0.528\text{MeV}\right)$. However, through constructive interference, direct capture below the resonance makes a non-negligible contribution to the reaction rate. We have determined this direct contribution by measuring the asymptotic normalization coefficient for ${}^{14}\mathrm{O}\to {}^{13}\mathrm{N}+p$. In our experiment, an $11.8\text{MeV}∕\text{nucleon}$ ${}^{13}\mathrm{N}$ radioactive beam was used to study the ${}^{14}\mathrm{N}\left({}^{13}\mathrm{N},{}^{14}\mathrm{O}\right){}^{13}\mathrm{C}$ peripheral transfer reaction, and the asymptotic normalization coefficient, ${\left(C_{p_{1∕2}}^{{}^{14}\mathrm{O}}\right)}^2=29.0\pm 4.3{\text{fm}}^{-1}$, was extracted from the measured cross section. The radiative capture cross section was estimated using an $R$-matrix approach with the measured asymptotic normalization coefficient and the latest resonance parameters. We find the $S$ factor for ${}^{13}\mathrm{N}\left(p,\gamma \right){}^{14}\mathrm{O}$ to be larger than previous estimates. Consequently, the transition from the cold to hot CNO cycle for novae would be controlled by the slowest proton capture reaction ${}^{14}\mathrm{N}\left(p,\gamma \right){}^{15}\mathrm{O}$.

We apply a microcanonical statistical model to investigate hadron production in $pp$ collisions. The parameters of the model are the energy $E$ and the volume $V$ of the system, which we determine via fitting the average multiplicity of charged pions, protons, and antiprotons in $pp$ collisions at different collision energies. We then make predictions of mean multiplicities and mean transverse momenta of all identified hadrons. Our predictions on nonstrange hadrons are in good agreement with the data, the mean transverse momenta of strange hadron as well. However, the mean multiplicities of strange hadrons are overpredicted. This agrees with canonical and grand-canonical studies, where a strange suppression factor is needed. We also investigate the influence of event-by-event fluctuations of the $E$ parameter.

A variational Monte Carlo analysis of recent binding energy data of the hypernucleus ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}6}\mathrm{He}$ has been made treating this as a six-body problem. A phenomenological central Urbana-type $\mathrm{\Lambda }\mathrm{\Lambda }$ potential which fits the new data, predicts a bound state for the charge symmetric pair ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}5}\mathrm{H}$, ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}5}\mathrm{He}$ and just or weakly bound state for ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}4}\mathrm{H}$ is obtained. A three-range Gaussian $\mathrm{\Lambda }\mathrm{\Lambda }$ potential phase equivalent to the Nijmegen model D over estimates by 25–80 % the binding energy of ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}6}\mathrm{He}$ and pair ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}5}\mathrm{H}$, ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}5}\mathrm{He}$ compared to an Urbana potential. The simulated potential predicts bound ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}4}\mathrm{H}$. The incremental $\mathrm{\Delta }{B}_{\mathrm{\Lambda }\mathrm{\Lambda }}$ value, leaving ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}{}^{\phantom{\mathrm{\Lambda }}4}\mathrm{H}$, for the above potentials is about half of that found in recent cluster model calculation which uses a $\mathrm{\Lambda }\mathrm{\Lambda }$ potential phase equivalent to the ND type in the Faddeev method.

In-beam $\gamma$-ray spectroscopy of ${}^{188}\mathrm{Pb}$ has been carried out using Gammasphere. Time-correlated $\gamma \text{−}\gamma$ coincidence methods have allowed the identification of new structures above and below the two-particle isomeric states. The detailed decay of the proposed $K^{\pi }=8^{-}$, $1\mu \mathrm{s}$ isomer has been established, together with a rotational band based on the isomer. Both decay and band properties confirm the association with a prolate deformation and the two-quasineutron $9∕2^{+}\left[624\right]\otimes 7∕2^{-}\left[514\right]$ configuration. The band structure identified above the ${11}^{-}$ isomer from the two-proton configuration $9∕2^{-}\left[505\right]\otimes 13∕2^{+}\left[606\right]$ has a moment of inertia similar to those of the bands known in heavier isotopes and to the one-quasiproton components, but the perturbations and in-band properties are not as expected for a simple, symmetric oblate deformation. This structure is fed by a $\left({19}^{-}\right)$ isomer. Possible configurations for this and other multiquasiparticle states are discussed in the context of multi-quasiparticle calculations for coexisting deformations. Low-spin structures populated partly from the decay of the $8^{-}$ isomer have also been identified. Several of these may be associated with proposed excited $0^{+}$ states. Their properties, including yrare-yrast $E0$ decays and gamma-ray branching ratios, are analyzed using band-mixing models. These and other analyses support a shape coexistence scenario, with some qualifications.

The angular momentum projected generator coordinate method, with the axially symmetric quadrupole moment as generating coordinate, has been applied to study the shape coexistence and quadrupole collectivity in the neutron-deficient isotopes ${}^{182–192}\mathrm{Pb}$. The finite range and density dependent Gogny interaction, with the parametrization $\mathrm{D}1\mathrm{S}$, has been used in the calculations. A good qualitative agreement with the available experimental results is found. Our results indicate that $Z=82$ remains, on the average, as a magic proton number for the considered nuclei and also support the experimental evidences for rotational bands built on coexisting low-lying states of oblate and prolate shapes.

Charmonium production and suppression in heavy-ion collisions at relativistic energies is investigated within different models, i.e., the comover absorption model, the threshold model, the statistical coalescence model, and the hadron-string-dynamics (HSD) transport approach. In HSD the charmonium dissociation cross sections with mesons are described by a simple phase-space parametrization including an effective coupling strength ${\mid M_i\mid }^2$ for the charmonium states $i={\chi }_c,J∕\psi ,{\psi }^{\prime }$. This allows inclusion of the backward channels for charmonium reproduction by $D\overline{D}$ channels—which are missed in the comover absorption and threshold model—employing detailed balance without introducing any new parameters. It is found that all approaches yield a reasonable description of $J∕\psi$ suppression in $\mathrm{S}+\mathrm{U}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions at Super Proton Synchrotron (SPS) energies. However, they differ significantly in the ${\psi }^{\prime }∕J∕\psi$ ratio versus centrality at SPS and especially at Relativistic Heavy-Ion Collider (RHIC) energies. These pronounced differences can be exploited in future measurements at RHIC to distinguish the hadronic rescattering scenarios from quark coalescence close to the quark-gluon plasma phase boundary.

New data, obtained from ${\beta }^{-}$ decay of ${}^{132}\mathrm{Sb}$ radioactive beam at HRIBF, has led to a significantly revised $\gamma$-decay scheme for ${}^{132}\mathrm{Te}$. The changes to the level scheme include a number of new, likely $2^{+}$, states below $2.5\text{MeV}$, which allows a test of very recent quasiparticle random phase approximation calculations with a density-dependent pairing force, and the removal of a $3^{-}$ state at $2281\text{keV}$, which resolves an incompatibility with the shell model and leads to a simple interpretation of the low-lying negative parity states.

Poincaré invariance, gauge invariance, conservation of parity, and time reversal invariance are respected in an impulse approximation evaluation of the handbag diagram. Proton wave functions, previously constrained by comparison with measured form factors, that incorporate the influence of quark transverse and orbital angular momentum (and the corresponding violation of proton helicity conservation) are used. Computed cross sections are found to be in reasonably good agreement with early measurements. The helicity correlation between the incident photon and outgoing proton, $K_{LL}$, is both large and positive at back angles. For photon laboratory energies of $⩽6\text{GeV}$, we find that $K_{LL}\ne A_{LL}$, and $D_{LL}\ne 1$.

We propose a microscopic effective interaction to treat pairing correlations in the ${}^{1}S_0$ channel. It is introduced by recasting the gap equation written in terms of the bare force into a fully equivalent pairing problem. Within this approach, the proposed interaction reproduces the pairing properties provided by the realistic AV18 force very accurately. Written in the canonical basis of the actual Bogolyubov transformation, the force takes the form of an off-shell in-medium two-body matrix in the superfluid phase multiplied by a BCS occupation number $2{\rho }_m$. This interaction is finite-ranged, nonlocal, total-momentum dependent, and density dependent. The factor $2{\rho }_m$ emerging from the recast of the gap equation provides a natural cutoff and makes zero-range approximations of the effective vertex meaningful. Performing such an approximation, the roles of the range and of the density dependence of the interaction can be disentangled. The isoscalar and isovector density dependences derived ab initio provide the pairing force with a strong predictive power when extrapolated toward the drip lines. Although finite ranged and nonlocal, the proposed interaction makes Hartree-Fock-Bogolyubov calculations of finite nuclei in coordinate space tractable. Through the two-basis method, its computational cost is of the same order as for a zero-range force.

Differential cross sections and a complete set of polarization observables have been measured for quasielastic $(\vec{p},\vec{n})$ reactions on ${}^{12}\mathrm{C}$ and ${}^{40}\mathrm{Ca}$ at a bombarding energy of $345\text{MeV}$. The laboratory momentum transfers are $q_{\text{lab}}\simeq 1.2$, 1.7, and $2.0{\text{fm}}^{-1}$ for ${}^{12}\mathrm{C}$ and $q_{\text{lab}}\simeq 1.7{\text{fm}}^{-1}$ for ${}^{40}\mathrm{Ca}$. In these momentum transfer regions, the isovector spin-longitudinal interaction is attractive where the one-pion exchange is dominant. The spin-longitudinal and spin-transverse polarized cross sections, $I{D}_q$ and $I{D}_p$, are deduced. The theoretically expected enhancement in the spin-longitudinal mode is observed at $q_{\text{lab}}\simeq 1.7$ and $2.0{\text{fm}}^{-1}$. The observed $I{D}_q$ is consistent with the pionic enhanced $I{D}_q$ evaluated in distorted wave impulse approximation (DWIA) calculations employing random phase approximation (RPA) response functions. The enhanced $I{D}_q$ implies the existence of a precursor to pion condensation in nuclei. On the other hand, the theoretically predicted quenching in the spin-transverse mode is not observed. The observed $I{D}_p$ is not quenched, but rather enhanced relative to that predicted via the $\mathrm{DWIA}+\mathrm{RPA}$ calculations. Two-step contributions are responsible in part for the enhancement of $I{D}_p$.

We study in detail the barrier distributions extracted from large-angle quasielastic scattering of heavy ions at energies near the Coulomb barrier. Using a closed-form expression for scattering from a single barrier, we compare the quasielastic barrier distribution with the corresponding test function for fusion. We examine the isocentrifugal approximation in coupled-channels calculations of quasielastic scattering and find that for backward angles it works well, justifying the concept of a barrier distribution for scattering processes. This method offers an interesting tool for investigating unstable nuclei. We illustrate this for the ${}^{32}\mathrm{Mg}+{}^{208}\mathrm{Pb}$ reaction, where the quadrupole collectivity of the neutron-rich ${}^{32}\mathrm{Mg}$ remains to be clarified experimentally.

The high spin structure of ${}^{91}\mathrm{Mo}$ with neutron and proton number close to magicity has been investigated using the ${}^{63}\mathrm{Cu}({}^{31}\mathrm{P},\mathit{xnyp})$ reaction at an incident beam energy of $125\text{MeV}$. The level at $E_x=3811\text{keV}$ has been assigned a negative parity based on our polarization measurements. In view of this change, the observed level structure for ${}^{91}\mathrm{Mo}$ so far does not have any negative parity sequence. More than 30 new transitions were observed and placed in the decay scheme, which has been extended up to spin of $J\sim 39∕2\hslash$ and an excitation energy of $E_x\sim 10\text{MeV}$. The energy spectrum bears signature of core breaking viz. presence of high energy $\left(E_{\gamma }\sim 2\text{MeV}\right)$ $\gamma$ rays originating due to excitation of nucleons across the shell gaps. The proposed level scheme is compared with large basis spherical shell model calculations. Excitation of protons across $Z=38$ shell dominates the level structure up to moderate spins i.e., $J\sim 27∕2\hslash$. Configurations arising due to excitation of a single $\nu g_{9∕2}$ across $N=50$ shell gap dominate the higher angular momentum $J⩾35∕2\hslash$ states.

Using Chandrasekhar’s $S$-type coupling between rotational and intrinsic vortical modes one may simply reproduce the Hartree-Fock-Bogoliubov (HFB) dynamical properties of rotating nuclei within Routhian HF calculations free of pairing correlations yet constrained on the relevant so-called Kelvin circulation operator. From the analogy between magnetic and rotating systems, one derives a model for the quenching of pairing correlations with rotation, introducing a critical angular velocity—analogous to the critical field in supraconductors—above which pairing vanishes. Taking stock of this usual model, it is then shown that the characteristic behavior of the vortical mode angular velocity as a function of the global rotation angular velocity can be modelized by a simple two parameter formula, both parameters being completely determined from properties of the band-head (zero-spin) HFB solution. From calculation in five nuclei, the validity of this modelized Routhian approach is tested. It is clearly shown to be very good in cases where the evolution of rotational properties is only governed by the coupling between the global rotation and the pairing-induced intrinsic vortical currents, otherwise it fails. It therefore provides a sound ground base for evaluating the importance of coupling of rotation with other modes (shape distortions, quasiparticle degrees of freedom).

An excitation function measurement has been performed over the laboratory range $52–94\text{MeV}$ investigating resonance phenomena in the single excitation ${}^{16}\mathrm{O}$ $\left({}^{16}\mathrm{O},{{}^{16}\mathrm{O}}^{*}\to {}^{12}\mathrm{C}_{\mathrm{g.s.}}+\alpha \right){}^{16}\mathrm{O}_{\mathrm{g.s.}}$ breakup reaction. A number of enhancements are observed in these excitation functions for excitation to the $4_1^{+}$, $10.35\text{MeV}$ and $4_2^{+}$, $11.09\text{MeV}$ excited states in ${}^{16}\mathrm{O}$. The overlap between these and previously measured enhancements is discussed. Excitation functions for the $2_2^{+}$, $9.84\text{MeV}$ and $2_3^{+}$, $11.52\text{MeV}$ excited states are also presented.

Predictions of the embedded Gaussian orthogonal random matrix ensemble of one plus two-body interactions, in the Gaussian domain, for the number of principal components and localization length, measuring complexity and chaos in transition strengths originating from an eigenstate with energy $E$, are tested successfully for the first time for $E2$ and $M1$ transition strengths. Shell-model results for the $2p1f$-shell nucleus ${}^{46}\mathrm{V}$ are used as the example.