Both simple and sophisticated models are frequently used in an attempt to understand how real nuclei breakup when subjected to large excitation energies, a process known as nuclear multifragmentation. Many of these models assume equilibrium thermodynamics and produce results often interpreted as evidence of a phase transition. This work examines one class of models and employs standard thermodynamical procedures to explore the possible existence and nature of a phase transition. The role of various terms, e.g., Coulomb and surface energy, is discussed.

We investigate quantal perturbations of the interferometric correlations of charged bosons by the Coulomb field of an instantaneous, charged source. The source charge increases the apparent source size by weakening the correlation at nonzero relative momenta. The effect is strongest for pairs with a small total momentum and is stronger for kaons than for pions of the same momenta. The low-energy data currently available are well described by this effect. A simple expression is proposed to account for the effect.

In Phys. Rev. C 58, 1679 (1998), A. J. Baltz and L. McLerran have derived an analytical expression for the electron-positron pair production by summing all higher orders in the high relativistic energy regime, and the result is in agreement with the expression obtained from the standard second-order perturbation theory by C. Bottcher and M. R. Strayer [Phys. Rev. D 39, 1330 (1989)]. Here we provide a calculation of higher order effects for multiple $e^{+}{e}^{-}$ pairs in relativistic heavy-ion collisions. We have found that for the multipair production cross section, the higher order effects substantially reduce the second-order perturbative results.

We study the changes produced by the deuteron on the QCD quark condensate by means of the Feynman-Hellmann theorem and find that the pion mass dependence of the pion-nucleon coupling could play an important role. We also discuss the relation between the many body effect of the condensate and the meson exchange currents, as seen by photons and pions. For pion probes, the many-body term in the physical amplitude differs significantly from that of soft pions, the one linked to the condensate. Thus no information about the many-body term of the condensate can be extracted from the pion-deuteron scattering length. On the other hand, in the Compton amplitude, the relationship with the condensate is a more direct one.

Truncation methods for the nuclear shell model are tested and compared in terms of properties of ${}^{28}\mathrm{Si},$ ${}^{28}\mathrm{Al},$ and ${}^{40}\mathrm{Mg}.$ Included are the traditional methods based on energy denominators and the number of particle-hole excitations, as well as a newer procedure which takes into account the two-body interactions. For nuclei with $T\gg 0$ the newer method is found appreciably better than the traditional methods, which are about equal. For nuclei with $N\approx Z$ there is little difference among the three methods.

Within the Glauber model the antikaon potential is evaluated from differential data on elastic $K^{-}C$ and $K^{-}\mathrm{Ca}$ scattering at momentum $p_K=800\mathrm{}\hspace{0.5em}\mathrm{MeV}/c.\mathrm{}$ We find that the imaginary part of the $K^{-}N$ scattering amplitude obtained from the $K^{-}A$ scattering data is close to the value given in free space. However, the real part of the forward scattering amplitude extracted from the scattering data on nuclei differs from the free space amplitude indicating a dropping of $\mathrm{Re}f\left(0\right)\mathrm{}$ at finite nuclear density. The perspectives of $K^{-}$ elastic scattering from symmetric nuclei at an antikaon momentum of $1.2\hspace{0.5em}\mathrm{GeV}/c$ are discussed.

Using Green’s function techniques, we derive expressions for the width of a proton decaying state in spherical and deformed nuclei. We show that the proton decay widths calculated by the “exact” expressions of Maglione et al. are equivalent to the distorted wave expressions of Bugrov et al., and that of Åberg et al. in the spherical case.

It is shown that three-body non-Borromean halo nuclei like ${}^{12}\mathrm{Be},$ ${}^{18}\mathrm{C},$ ${}^{20}\mathrm{C},$ considered as neutron-neutron-core systems, have p-wave virtual states with energy of about 1.7 times the corresponding neutron-core binding energy. We use a renormalizable model that guarantees the general validity of our results in the context of short range interactions.

The effective interaction method, traditionally used in the framework of a harmonic oscillator basis, is applied to the hyperspherical formalism of few-body nuclei $(A=3\mathrm{}-6)$. The separation of the hyperradial part leads to a state dependent effective potential. Undesirable features of the harmonic oscillator approach associated with the introduction of a spurious confining potential are avoided. It is shown that with the present method one obtains an enormous improvement of the convergence of the hyperspherical harmonics series in calculating ground state properties, excitation energies, and transitions to continuum states.

The quasiparticle random phase approximation (QRPA) equations are solved taking into account the Pauli principle at the expectation value level, and allowing changes in the mean field occupation numbers to minimize the energy while having the correct number of particles in the correlated vacuum. The study of Fermi $\mathrm{pn}$ excitations in ${}^{76}\mathrm{Ge}$ using a realistic Hilbert space shows that the pairing energy gaps in the modified mean field are diminished up to one half of the experimental value when strong proton-neutron correlations are present. Additionally, the Ikeda sum rule for Fermi transitions is violated due to the lack of scattering terms in the phonon operators. These results call for a critical revision of the double $\beta$ decay half-lives estimated using the QRPA extensions when standard QRPA calculations collapse.

The ${(}^3\mathrm{He},t)$ reaction on ${}^{124}\mathrm{Sn}$ at ${E(}^3\mathrm{He})=199\mathrm{}\mathrm{MeV}$ and the subsequent decay by neutron emission at backward angles were studied in an attempt to distinguish isovector monopole strength (spin-flip and non-spin-flip) at excitation energies above 25 MeV from the nonresonant continuum. The present approach is based on the assumption that a large fraction of the contributions to the continuum result from quasifree processes and breakup-pickup processes which leave the nucleus in low-lying excited states below the threshold for neutron emission. It was found, however, that even at high “apparent” excitation energies (above 30 MeV) the branching ratio for decay by neutrons was as high as $\sim 50\%,$ indicating that a large part of the nonresonant continuum may not be due to quasifree processes involving valence neutrons only. No evidence for monopole strength at high excitation energies was found, although the experiment had sufficient sensitivity and accuracy to detect isovector monopole strength based on theoretical predictions calculated in the framework of normal-mode collective excitations and the distorted-wave Born approximation.

The E885 Collaboration utilized the $1.8\hspace{0.5em}\mathrm{GeV}{/cK}^{-}$ beam line at the Alternating Gradient Synchrotron (AGS) to accumulate greater than 10 times the world’s existing data sample of ${(K}^{-}{,K}^{+})$ events on carbon. A total of about $3\times {10}^5\hspace{0.5em}{(K}^{-}{,K}^{+})$ events were collected and analyzed. $\Xi$ hypernuclear states are expected to be produced through the reaction $K^{-}{+}^{12}\overrightarrow{C}{K}^{+}{+}_{\Xi }^{12}\mathrm{Be}.$ A signal could also result from direct production of ${}_{\Lambda }^{11}\mathrm{Be}+\Lambda$ without a distinct $\Xi$ intermediate state. The measured missing-mass spectrum indicates the existence of a signal below the threshold for free ${\Xi }^{-}$ production that cannot be explained by background or effects of limited resolution. Although the resolution was not sufficient to resolve discrete hypernuclear states, the excess of events in the region of missing mass, kinematically inaccessible in free ${\Xi }^{-}$ production, can be compared with theoretical predictions for ${}_{\Xi }^{12}\mathrm{Be}$ production. Reasonable agreement between the data and theory is achieved by assuming a $\Xi$-nucleus potential well depth ${\mathrm{V}}_{0\Xi }$ of about 14 MeV within the Woods-Saxon prescription.

We derive the effective coarse-grained field equation for the scalar condensate of the linear sigma model in a simple and straightforward manner using linear response theory. The dissipative coefficient is calculated consistently at tree level on the basis of the physical processes of sigma-meson decay and of thermal sigma mesons and pions knocking sigma mesons out of the condensate. The field equation is solved for hot matter undergoing either one- or three-dimensional expansion and cooling in the aftermath of a high energy nuclear collision. The results show that the time constant for returning the scalar condensate to thermal equilibrium is of order $2\mathrm{fm}/c.\mathrm{}$

In this paper we study the modification of the properties of the nucleon in the nucleus within the quark-soliton model. This is a covariant, dynamical model, which provides a nonlinear representation of the spontaneously broken $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R$ symmetry of QCD. The effects of the nuclear medium are accounted for by using the Wigner-Seitz approximation and therefore reducing the complex many-body problem to a simpler single-particle problem. We find a minimum in the binding energy at finite density, a change in the isoscalar nucleon radius, and a reduction of the in-medium pion decay constant. The latter is consistent with a partial restoration of chiral symmetry at finite density, which is predicted by other models.

For ${}^{54}\mathrm{Mn}$ there is a discrepancy between the $Q_{\mathrm{EC}}$ obtained from the endpoint energy of the internal bremsstrahlung (IB) spectrum which accompanies the electron capture decay ${(Q}_{\mathrm{EC}}=1353\mathrm{}\pm 8\mathrm{keV})$ and that obtained from the accepted mass differences ${(Q}_{\mathrm{EC}}=1377\mathrm{}\pm 1\mathrm{keV}).\mathrm{}$ This Q value is needed to deduce the partial-half life of the astrophysically interesting ${\beta }^{-}$ decay of ${}^{54}\mathrm{Mn}$ from the recently measured ${\beta }^{+}$ partial half-life. To resolve this discrepancy, we have remeasured the endpoint energy of the IB spectrum, by recording coincidences between the IB and the 835-keV $\gamma$ ray, both detected in Compton-suppressed Ge detectors. The $Q_{\mathrm{EC}}$ we deduce is $1379\pm 8\mathrm{keV},$ in agreement with the accepted mass differences.

The ${}^{208}\mathrm{Pb}{\mathrm{}(n,p)\mathrm{}}^{208}\mathrm{Tl}$ reaction cross section has been measured between 30 and 70 MeV neutron energy by the activation method. The results are compared with the predictions of a schematic model which includes contributions from direct reactions and compound nucleus formation.

The systematics of the lowered energies of the $1^{-}$ states and the lowered hindrance factors in α decay populating these $1^{-}$ states suggest an increased octupole correlation for Pu and U nuclei with 144 and 146 neutrons.

Excited states have been identified in the very neutron-deficient ${}^{119}\mathrm{Ba}$ nucleus. Two bands have been observed, which are likely to be based on $h_{11/2}$ and ${(g}_{7/2}{d}_{5/2})$ neutron orbitals. Despite this being the first observation of excited states in ${}^{119}\mathrm{Ba},$ the bands extend to $\mathrm{}(75/2)\mathrm{}ħ$ and $\mathrm{}(79/2)\mathrm{}ħ,$ respectively. The bands have been assigned to ${}^{119}\mathrm{Ba}$ using gamma-recoil and gamma–x-ray coincidences. Several quasiparticle alignments have been identified, involving neutron ${(h}_{11/2}{)}^2$ and proton ${(h}_{11/2}{)}^2$ aligned configurations. Furthermore, the bands show features which are reasonably consistent with smooth band termination at high spin. Theoretical results for ${}^{119}\mathrm{Ba}$ are discussed within the framework of cranked Woods-Saxon and Nilsson-Strutinsky calculations.

High-spin states in ${}^{131}\mathrm{Nd}$ were populated in the reaction ${}^{94}\mathrm{Mo}{(}^{40}\mathrm{Ca},2pn)$ at a beam energy of 180 MeV. Over 170 new transitions were placed in a level scheme that consists of seven rotational structures. The bands were given configuration assignments based on their $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios (for the strongly coupled bands), aligned angular momentum, observed band crossings, and signature splitting. Several quasiparticle alignments were observed in the bands and compared with predictions from the cranked shell model. Three-band mixing calculations were performed in order to interpret the low-spin interaction observed in the [411]1/2 band. An examination of the signature splitting for the [541]1/2 bands in ${}^{129,131,133}\mathrm{Nd}$ revealed information regarding the parentage of the orbital as well as a signature inversion at higher spin.