Caloric curves are evaluated via a sharp microcanonical model using seven isotopic thermometers for three representative sample nuclei. A dispersive character of the isotopic caloric curves and a monotonically increasing deviation of most of them from the microcanonical caloric curve caused by finite size effects are pointed out. A procedure of calibrating the nuclear thermometers of the microcanonical caloric curve is proposed. A set of calibrating parameters independent of the system size and excitation energy is found for each considered isotopic thermometer. The obtained parametrization is used for reevaluating the main experimental caloric curves obtained so far.

In heavy-ion collisions, $J/\psi$ and Drell-Yan production are expected to be affected by nuclear modifications to the free nucleon structure functions. If these modifications, referred to here as shadowing, are proportional to the local nuclear density, the per nucleon cross sections will depend on centrality. Differences in quark and gluon shadowing will lead to a new source of impact parameter dependence of the $J/\psi$ to Drell-Yan production ratio. We calculate this ratio in the CERN NA50 acceptance with several shadowing parametrizations to explore its centrality dependence.

Recent photoproduction measurements of the ${\rho }^0$ vector meson in the nuclear medium have revealed a substantial reduction in its mass from the vacuum value. The decay of the ${\rho }^0$ within the strong nucleonic field at low relative ${\rho }^0$-$N$ momenta, and the collective $N^{*}{\mathrm{}\left(1520\right)N}^{-1}$ excitation, have both been presented previously as plausible explanations. In this Rapid Communication we show that the reduction can be explained through a bound ${\rho }^0$-nucleus state. The depth of the potential required to produce the bound state is consistent with that extracted from Dirac phenomenology using Brown-Rho scaling.

The three-body breakup ${}^6{\overrightarrow{\mathrm{He}}}^4\mathrm{He}+n+n$ is studied experimentally, using a secondary ${}^6\mathrm{He}$ ion beam of 240 MeV/nucleon incident on carbon and lead targets. Integrated cross sections for one- and two-neutron knockout and differential cross sections $d\sigma {/dE}^{*}$ and $d\sigma /d\vartheta$ for inelastic nuclear or electromagnetic excitations into the ${}^6\mathrm{He}$ continuum are presented. The $E$1-strength distribution is deduced from electromagnetic cross sections and is found to exhaust $(10\mathrm{}\pm 2)\%$ of the energy-weighted Thomas-Reiche-Kuhn sum rule or $(40\mathrm{}\pm 8)\%$ of the cluster sum rule for excitation energies below 5 MeV. Both the energy-weighted and non-energy-weighted dipole cluster sum rules are almost exhausted integrating the strength up to 10 MeV, a fact from which the root-mean-square distance between the $\alpha$ core and the two valence neutrons of $r_{\alpha -2n}=(3.36\mathrm{}\pm 0.39)$ fm is derived. The known $I^{\pi }{=2\mathrm{}}^{+}$ (1.80 MeV) resonance in ${}^6\mathrm{He}$ is observed in nuclear inelastic scattering; model-dependent values of the quadrupole deformation parameter ${\delta }_2=(1.7\mathrm{}\pm 0.3)$ fm or ${B(E2,0\mathrm{}}^{+}\to 2^{+})=(3.2\mathrm{}\pm {0.6)e}^2\hspace{0.5em}{\mathrm{fm}}^4$ are derived. No clear signature could be obtained for predicted higher-lying $2^{+}$ resonances, but low-lying continuum strength of multipolarity other than dipole, likely of monopole and quadrupole multipolarity, is indicated by the data. Two-body correlations in the decaying ${}^4\mathrm{He}+n+n$ system are investigated. The astrophysical relevance of the data with regard to the two-neutron capture process ${}^4\mathrm{He}(2n,\gamma {)}^6\mathrm{He}$ is briefly discussed.

We present a unified description of the relativistic $\pi \mathrm{NN}$ and $\gamma \pi \mathrm{NN}$ systems where the strong interactions are described nonperturbatively by four-dimensional integral equations. A feature of our approach is that the photon is coupled in all possible ways to the strong interaction contributions. Thus the hadronic processes $N\overrightarrow{N}NN,\hspace{0.5em}N\overrightarrow{N}\pi d,\hspace{0.5em}\pi \overrightarrow{d}\pi d,$ etc. and corresponding electromagnetic processes $N\overrightarrow{N}\gamma NN,$ $\gamma \overrightarrow{d}NN,$ $\gamma d$ $\to \pi d,$ $e\overrightarrow{d}ed,$ $e\overrightarrow{d}{e}^{\prime }\pi d,$ etc., are described simultaneously within the one model of strong interactions. Our formulation obeys two and three-body unitarity, and as photons are coupled everywhere in the strong interaction model, gauge invariance is implemented in the way prescribed by quantum field theory. Our formulation is also free from the overcounting and undercounting problems plaguing four-dimensional descriptions of $\pi \mathrm{NN}-\mathrm{like}$ systems. The unified description is achieved through the use of the recently introduced gauging of equations method.

We use a three-body model to investigate breakup reactions of ${}^{11}\mathrm{Li}\hspace{0.5em}{(n+n+}^9\mathrm{Li})$ on a light target. The interaction parameters are constrained by known properties of the two-body subsystems, the ${}^{11}\mathrm{Li}$ binding energy and fragmentation data. The remaining degrees of freedom are discussed. The projectile-target interactions are described by phenomenological optical potentials. The model predicts dependence on beam energy and target, differences between longitudinal and transverse momentum distributions, and provides absolute values for all computed differential cross sections. We give an almost complete series of observables and compare with corresponding measurements. Remarkably good agreement is obtained. The relative neutron-${}^9\mathrm{Li}\hspace{0.5em}p$-wave content is about 40%. A p-resonance, consistent with measurements at about 0.5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the momentum distributions are insensitive to target and beam energy with a tendency to increase towards lower energies. The transverse momentum distributions are broader than the longitudinal ones due to the diffraction process. The absolute values of the cross sections follow the neutron-target cross sections and increase strongly for beam energies decreasing below 100 MeV/nucleon.

We examine the scattering of charged pions from the trinucleon system at a pion energy of 180 MeV. The motivation for this study is the structure seen in the experimental angular distribution of back-angle scattering for ${\pi }^{+}{-}^3\mathrm{He}$ and ${\pi }^{-}{-}^3\mathrm{H}$ but for neither ${\pi }^{-}{-}^3\mathrm{He}$ nor ${\pi }^{+}{-}^3\mathrm{H}$. We consider the addition of a double spin flip term to an optical model treatment and find that, though the contribution of this term is non-negligible at large angles for ${\pi }^{+}{-}^3\mathrm{He}$ and ${\pi }^{-}{-}^3\mathrm{H}$, it does not reproduce the structure seen in the experiment.

High-spin states in doubly odd ${}^{176}\mathrm{Re}$ were investigated by means of in-beam $\gamma$-ray spectroscopy techniques using the multidetector array GASP. Excited states of ${}^{176}\mathrm{Re}$ were populated using the ${}^{165}\mathrm{Ho}{(}^{16}\mathrm{O},5n)$ reaction at a beam energy of 101 MeV. Seven rotational bands have been observed and their configurations have been discussed. Alignments, band crossing frequencies, and electromagnetic properties have been analyzed in the framework of the cranking model. Signature inversion phenomena in the $\pi h_{11/2}\otimes \nu i_{13/2}$ and $\pi h_{9/2}\otimes \nu i_{13/2}$ structures are discussed. In the latter case signature inversion is traced to a large repulsive matrix element of the $p-n$ force acting in the maximally aligned $J=11\mathrm{}$ state.

Several new high-spin states are observed in the prompt $\gamma$-rays emitted from the neutron-rich, odd-$Z$ ${}^{145,147}\mathrm{La}$ fragments produced in the spontaneous fission of ${}^{252}\mathrm{Cf}.$ Alternating parity bands are extended up to spins 41/2 and 43/2 in ${}^{145,147}\mathrm{La},$ respectively. A new band completes the evidence for two sets of parity doublets expected for octupole correlations. Eight $B\left(E1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios (four new) between two bands in ${}^{145}\mathrm{La}$ are all essentially constant and somewhat larger than similar ratios in ${}^{143,144}\mathrm{Ba},$ where stable octupole deformation and/or correlations are reported. The new ratios out of the ${31/2}^{-}$ levels in both nuclei show a sharp spike compared to other states, presumably from a strong reduction in $E2\mathrm{}$ strengths in this backbending region. In ${}^{145}\mathrm{La},$ collective bands show competition and coexistence between symmetric and asymmetric shapes. Band crossings occur in both nuclei around $ħ\omega \approx 0.26–0.30\hspace{0.5em}\mathrm{MeV}.$ Their backbends are associated with the alignment of two $i_{13/2}$ neutrons according to cranked shell model calculations.

Yrast states of ${}^{106}\mathrm{Sb}$ have been investigated in the ${}^{54}\mathrm{Fe}{(}^{58}\mathrm{Ni},\alpha pn)$ reaction using in-beam $\gamma$-spectroscopic methods and in the ${}^{50}\mathrm{Cr}{(}^{58}\mathrm{N}\mathrm{i},pn)$ reaction performing delayed $\gamma$ and conversion electron studies. A new isomeric state was found at 103 keV with $t_{1/2}=232\mathrm{}\left(21\right)\mathrm{}\hspace{0.5em}\mathrm{ns}.$ The number of states and transitions in the proposed level scheme have been doubled. The experimental results are discussed within the framework of the shell model.

The ${}^{72}\mathrm{As}$ nucleus was studied via the $(\alpha ,n\gamma )$ reaction at 14.2 MeV bombarding energy. Single $\gamma -,\gamma \gamma$-coincidence, and internal conversion electron spectra were measured with Ge(HP) $\gamma$-ray and superconducting magnetic lens plus Si(Li) electron spectrometers. On the basis of the internal conversion coefficients $\mathrm{of}{}^{72}\mathrm{As}$ transitions, parities of the medium-spin levels up to 1.4 MeV excitation energy were determined, resulting in unambiguous parities also for the heads of the bands observed previously. The states observed were assigned to proton-neutron multiplets on the basis of their decay properties. The energy splittings of the observed multiplets are in accordance with the prediction of the previous interacting boson-fermion-fermion model (IBFFM) calculations using a transitional core lying between the vibrational SU(5) and $\gamma$-soft O(6) limits, except that of the $\pi g_{9/2}\nu g_{9/2}$ multiplet, which was described using the deformed SU(3) core in the present IBFFM calculations. Such a core structure is in accordance with previous particle-rotor and Hartree-Fock-Bogoliubov calculations.

High-spin states were populated in ${}^{134}\mathrm{Ce}$ using the ${}^{124}\mathrm{Sn}{(}^{16}\mathrm{O},6n)$ reaction at beam energies of 120 and 125 MeV. We have observed three new, weakly populated, regularly spaced rotational bands, one with an energy spacing of $\sim 60$ keV and two with a spacing of $\sim 100$ keV. These bands are compared with similar structures in neighboring nuclei. The experimental data are also compared with total Routhian surface and cranked Woods-Saxon calculations. The band with the narrower energy spacing is assigned as a highly deformed structure with a $\nu [{(i}_{13/2}{)}^3\otimes f_{7/2}]$ configuration relative to the $N=72\mathrm{}$ shell gap at a deformation of ${\beta }_2\sim \mathrm{0.4.}$ The remaining two structures are thought to result from triaxial configurations with ${\beta }_2\sim 0.2$ and $\gamma \sim -30°.$

High-spin states in ${}^{75}\mathrm{Br}$ were populated to investigate shape competition and shape coexistence phenomena in the single and three-quasiparticle regions. The thin-target experiment ${}^{48}\mathrm{Ti}{(}^{30}\mathrm{Si}{,p2n)}^{75}\mathrm{Br}$ at 90 MeV was performed using the FSU Tandem-LINAC accelerator facility, and the FSU-PITT array of 10 Compton-suppressed Ge detectors for the collection of $\gamma -\gamma$ coincidence data. Construction of level schemes and assignments of decays, excitation energies, spins, and parities were achieved through examination of coincidence data, relative intensity measurements, and angular correlation analysis. A rotational sequence with band-head spin-parity $J^{\pi }={\frac{9}{2}}^{+}$ was found and is compared to a similar band in ${}^{77}\mathrm{Br}.$ A negative-parity three-quasiparticle band exhibiting rigid rotation was also discovered. In total, 65 new transitions and 36 new excitation states were added to the level scheme. Cranked-shell, Hartree-Fock-Bogoliubov, and particle-rotor coupling models are used in the interpretation.

High-spin spectroscopy on odd-odd ${}^{164}\mathrm{Tm}$ has produced new illustrations of departures from the predictions of principal-axis cranking. Among the nine strongly coupled rotational bands observed, four are assigned to the parallel and antiparallel couplings of two configurations $\pi h_{11/2}\nu i_{13/2}$ and $\pi g_{9/2}\nu i_{13/2}.$ This represents the first time that the high-spin properties of both couplings can be explored. We find that the measured $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ values in the $K=1\left(\uparrow \downarrow \right)$ coupling of $\pi h_{11/2}\nu i_{13/2}$ are 50% larger than those in the $K=6\mathrm{}$ (↑↑) coupling, and represent the largest seen in this nucleus. Tilted-axis cranking calculations successfully explain the $M1/E2\mathrm{}$ ratios in these two bands, while the particle-rotor calculations did not reproduce the full low-K enhancement. No inversion in the signatures of the $K=6\mathrm{}\pi h_{11/2}\nu i_{13/2}$ band is observed, but there is a small inversion in the $K=1\mathrm{}$ coupling up to $I=17\mathrm{}ħ$ and a large inversion in the $\pi h_{9/2}\nu i_{13/2}$ band up to $I=19\mathrm{}ħ.$ Remarkably, particle-rotor calculations with a $p-n$ interaction included are able to reproduce these inversions. A stronger $p-n$ interaction is needed to explain an inversion in the $\pi d_{3/2}\nu i_{13/2}$ band.

We have investigated the ground-state properties of carbon isotopes in the framework of the relativistic mean-field (RMF) theory. RMF calculations have been performed with the nonlinear scalar self-coupling of the $\sigma$ meson using an axially symmetric deformed configuration. We have also introduced the vector self-coupling of the $\omega$ meson for the deformed mean-field calculations. The results show that the RMF predictions on radii and deformations are in good agreement with the available experimental data. It is shown that several carbon isotopes possess a highly deformed shape akin to a superdeformation. The single-particle structure of nuclei away from the stability line has been discussed with a view to understand the properties near the neutron drip line. Predictions of properties of carbon isotopes away from the stability line are made.

The energies and widths of resonance states are determined by the analytic continuation of bound-state energies as functions of a potential strength parameter (“the coupling constant”). Various numerical examples show the applicability of the method to systems decaying to two- and three-body channels. The examples include unbound states of the nuclei ${}^5\mathrm{He},$ ${}^5\mathrm{Li},$ ${}^9\mathrm{Be},$ and ${}^9\mathrm{B},$ described in $\alpha +N$ and $\alpha +\alpha +N$ microscopic cluster models. Some states considered are controversial. Here they are well defined, and their questionable features are understood to arise from their proximity to the complex-energy region of unphysical resonances with negative energies and positive widths.

The effects of the residual proton-neutron interactions on bandcrossing features are studied by means of shell model calculations for nucleons in a high-$j$ intruder orbital. The presence of an odd-nucleon shifts the frequency of the alignment of two nucleons of the other kind along the axis of rotation. It is shown that the anomalous delayed crossing observed in nuclei with aligning neutrons and protons occupying the same intruder subshell can be partly attributed to these residual interactions.

We extend the effective field theory approach which successfully describes ordinary nuclei and nuclear matter to incorporate strangeness in nuclear structure. The central object is a chiral effective Lagrangian involving the baryon octet, the Goldstone boson octet, the vector meson octet, and a light scalar singlet. According to the rules of effective field theory, we include all interaction terms (up to a given order of truncation) that are consistent with the underlying symmetries of QCD. We develop a mean-field approximation and study nuclear matter as a simple model for multistrange systems. A D-type Yukawa coupling between baryons and vector mesons leads to $\Lambda -{\Sigma }^0$ flavor mixing in the nuclear medium. We study flavor oscillations in the nuclear matter ground state which are closely related to the phenomenon of neutrino oscillations.

We discuss a variational approach to collective excitations in a boson formalism based on quasiparticles. Bosons are defined in correspondence with pairs of quasiparticles and boson images of fermion operators are constructed by means of a mapping procedure of Marumori-type. Phonons of the type used within the random phase approximation (RPA) are introduced as Bogoliubov transformations of these bosons. The variables entering into the definition of these phonons as well as of the quasiparticle operators are fixed simultaneously by minimizing the expectation value of the boson Hamiltonian in the vacuum of the phonons. The approach is tested within an exactly solvable two-level model which is characterized by a pairing Hamiltonian. A quite good agreement is found for the energies of the ground state and of the first $0^{+}$ excited state. The comparison with the Bardeen-Cooper-Schrieffer method and the quasiparticle RPA as well as with some recent self-consistent RPA-type approaches is discussed.

The core breakup or distortion effects in the neutron-halo nucleus ${}^6\mathrm{He}$ are studied with an extended microscopic $\alpha +n+n$ three-cluster model, in which the core particle, i.e., the $\alpha$ cluster is described as a $3N+N$ two-cluster system. The two-cluster description improves the tail behavior of the $\alpha$ particle with respect to the standard $0s$ harmonic-oscillator shell-model description, and makes the first excited state of the $\alpha$ particle realistic. The allowance for the core breakup in ${}^6\mathrm{He}$ enhances not only the binding energy but also the probability of the $t+t$ component. This model gives a binding energy and $t+t$ probability that are similar to the $\{\alpha +n+n;t+t\}$ model, and both can reproduce the very small binding energy of ${}^6\mathrm{He}.$ The inclusion of the $t+t$ channel deepens the binding substantially only when added to the conventional $\alpha +n+n$ model; when the extended three-cluster model is augmented by $t+t,$ its contribution is insignificant. Our results show that, for a weakly bound system such as a halo nucleus, the core internal motion must be treated realistically since the tail behavior of the core affects the binding mechanism of the halo nucleons.