The rates of neutrino pair emission by nucleon-nucleon (NN) bremsstrahlung are calculated with the inclusion of the full contribution from a nuclear one pion exchange potential (OPEP). We compute the contributions from the neutron-neutron (nn), proton-proton (pp), and neutron-proton (np) processes for physical conditions encountered in supernovae and neutron stars, both in the degenerate (D) and nondegenerate (ND) limits. We find a significant reduction of these rates, especially for the nn and pp processes, in comparison with the case when the whole nuclear contribution was replaced by constants, representing the high-momentum limits of the expressions of the nuclear potential. Furthermore, we also perform the calculations by including contributions due to the $\rho$ meson exchange between nucleons, in the OPEP. This may be relevant for processes produced in the inner core of neutron stars, where the density may exceed several times the standard nuclear density, and the short-range part of the NN interaction should be taken into account. These corrections lead to an additional suppression of the neutrino emission rates between (8 and 36)%, depending on the process [nn (pp) or np] and physical conditions (temperature and degeneracy of the nucleons).

The experimental data concerning transient-field strengths for ions with $6⩽Z⩽16$ moving in $\mathrm{Fe}$ and $\mathrm{Gd}$ hosts are summarized for ion velocities greater than $\frac{1}{2}Z{v}_0$. Based on model expectations, a parametrization of the field strength is proposed. For both $\mathrm{Fe}$ and $\mathrm{Gd}$ hosts the form is $B_{\text{tf}}(v,Z)=A{Z}^P{(v∕Z{v}_0)}^2{e}^{-{(v∕Z{v}_0)}^4∕2}$, where $A$ and $P$ are determined by fitting data. The implications of the parameter values for understanding the physics of the transient field are discussed along with applications to the measurement of excited-state $g$ factors in exotic nuclei produced by intermediate-energy fragmentation reactions.

We investigate a random matrix model [Phys. Rev. C 65, 024302 (2002)] for the decay-out of a superdeformed band as a function of the parameters: ${\Gamma }^{\downarrow }∕{\Gamma }_S$, ${\Gamma }_N∕D$, ${\Gamma }_S∕D$, and $\Delta ∕D$. Here ${\Gamma }^{\downarrow }$ is the spreading width for the mixing of a superdeformed (SD) state $\mid 0⟩$ with a normally deformed (ND) doorway state $\mid d⟩$, ${\Gamma }_S$ and ${\Gamma }_N$ are the electromagnetic widths of the SD and ND states, respectively, $D$ is the mean level spacing of the compound ND states and $\Delta$ is the energy difference between $\mid 0⟩$ and $\mid d⟩$. The maximum possible effect of a transition from ordered to chaotic states is inferred from analytical and numerical calculations of the decay intensity in the limiting cases for which the ND states obey Poisson and GOE statistics. Our results show that the sharp attenuation of the decay intensity cannot be explained solely by a transition from ordered to chaotic states.

Within the framework of an extended optical model, simultaneous ${\chi }^2$ analyses are performed for elastic scattering and fusion cross-section data for ${}^9\mathrm{Be}+{}^{209}\mathrm{Bi}$ and ${}^6\mathrm{Li}+{}^{208}\mathrm{Pb}$ systems, both involving loosely bound projectiles, at near-Coulomb-barrier energies to determine the polarization potential as decomposed into direct reaction $\left(\text{DR}\right)$ and fusion parts. We show that both $\text{DR}$ and fusion potentials extracted from ${\chi }^2$ analyses separately satisfy the dispersion relation, and that the expected threshold anomaly appears in the fusion part. The $\text{DR}$ potential turns out to be a rather smooth function of the incident energy, and has a magnitude at the strong absorption radius much larger than the fusion potential, explaining why a threshold anomaly has not been seen in optical potentials deduced from fits to the elastic-scattering data without such a decomposition. Using the extracted $\text{DR}$ potential, we examine the effects of projectile breakup on fusion cross sections ${\sigma }_F$. The observed suppression of ${\sigma }_F$ in the above-barrier region can be explained in terms of the flux loss due to breakup. However, the observed enhancement of ${\sigma }_F$ in the subbarrier region cannot be understood in terms of the breakup effect. Rather, the enhancement can be related to the $Q$ value of the neutron transfer within the systems, supporting the ideas of Stelson et al. [Phys. Lett. B 205, 190 (1988); Stelson et al.Phys. Rev. C 41, 1584 (1990)] that subbarrier fusion starts to occur when the colliding ions are at a distance where the barrier against the flow of the valence neutrons disappears and thus neutron exchange can take place freely.

The exclusive $K^{+}$ meson production in a proton-nucleus collision, leading to two body final states, is investigated in a fully covariant two-nucleon model based on the effective Lagrangian picture. The explicit kaon production vertex is described via creation, propagation, and decay into relevant channel of $N^{*}\left(1650\right)$, $N^{*}\left(1710\right)$, and $N^{*}\left(1720\right)$ intermediate baryonic states in the initial collision of the projectile nucleon with one of its target counterparts which is modeled by the one-pion exchange process. The calculated cross sections show strong sensitivity to the medium effects on pion propagator and to the final hypernuclear state excited in the reaction.

Movement of Efimov states in ${}^{20}\mathrm{C}$ as a result of increasing the $n\text{−}{}^{18}\mathrm{C}$ binding energy from about $100\text{to}500\mathrm{keV}$ is studied in a three body model for ${}^{20}\mathrm{C}$, assumed to be $n+n+{}^{18}\mathrm{C}$ system, employing separable potentials for the $n\text{−}n$ and $n\text{−}{}^{18}\mathrm{C}$ binary subsystems. The computational analysis shows that for small values of energies (< about $120\mathrm{keV}$) which are just necessary to bind the two body $\left(n\text{−}{}^{18}\mathrm{C}\right)$ system, there could be more than one bound Efimov states. But the states are found to go on disappearing one by one as the binding energy is increased beyond $200\mathrm{keV}$. As originally pointed out by Amado and Noble [Phys. Rev. D 5, 1992 (1972)], the Efimov states move into the unphysical sheet associated with the two body unitarity cut on increasing the strength of the binary interaction to bind the two body system. By undertaking a detailed study of the scattering of neutron on a bound $\left(n\text{−}{}^{18}\mathrm{C}\right)$ system, we find that these states move over to the physical scattering region causing a resonance in $n\text{−}{}^{19}\mathrm{C}$ scattering around neutron incident energy of $1.6\mathrm{keV}$, having a width of about $0.25\mathrm{keV}$.

We study the isoscalar $(T=0)$ and isovector $(T=1)$ pairing correlations in $N=Z$ nuclei. They are estimated from the double difference of binding energies for odd-odd $N=Z$ nuclei and the odd-even mass difference for the neighboring odd-mass nuclei, respectively. The empirical and BCS calculations based on a $T=0$ and $T=1$ pairing model reproduce well the almost degeneracy of the lowest $T=0$ and $T=1$ states over a wide range of even-even and odd-odd $N=Z$ nuclei. It is shown that this degeneracy is attributed to competition between the isoscalar and isovector pairing correlations in $N=Z$ nuclei. The calculations give an interesting prediction that the odd-odd $N=Z$ nucleus ${}^{82}\mathrm{Nb}$ has possibly the ground state with $T=0$.

The rate at which nuclei are produced in a multistep laser ionization process is calculated as a function of the resonant laser excitation frequency. The model enables the fitting of the hyperfine spectra obtained by resonantly exciting and ionizing beams of (short-lived) nuclei. The fit parameters are the nuclear dipole and quadrupole moments, an isotope/isomer shift and the laser powers. The dressed-states approach for the interaction of laser light with an ensemble of atoms and the influence of the ionizing step as an irreversible process in a two-level system allow a very clear understanding of the physical process. In addition, it is seen that the yield of the on-resonance produced ions is sensitive to the angular momenta of the electron levels and to the nuclear spin.

The observational consequences of certain broken symmetries in a thermalized quark gluon plasma are elucidated. The signature under study is the spectrum of dileptons radiating from the plasma, through gluon fusion. Being a pure medium effect, this channel is nonvanishing only in plasmas with explicitly broken charge conjugation invariance. The emission rates are also sensitive to rotational invariance through the constraints imposed by Yang’s theorem. This theorem is interpreted in the medium via the destructive interference between various multiple scattering diagrams obtained in the spectator picture. Rates from the fusion process are presented in comparison with those from the Born term.

The finite temperature Brueckner-Hartree-Fock approach is extended by introducing a microscopic three-body force. In the framework of the extended model, the equation of state of hot asymmetric nuclear matter and its isospin dependence have been investigated. The critical temperature of liquid-gas phase transition for symmetric nuclear matter has been calculated and compared with other predictions. It turns out that the three-body force gives a repulsive contribution to the equation of state which is stronger at higher density and as a consequence reduces the critical temperature of liquid-gas phase transition. The calculated energy per nucleon of hot asymmetric nuclear matter is shown to satisfy a simple quadratic dependence on asymmetric parameter $\beta$ as in the zero-temperature case. The symmetry energy and its density dependence have been obtained and discussed. Our results show that the three-body force affects strongly the high-density behavior of the symmetry energy and makes the symmetry energy more sensitive to the variation of temperature. The temperature dependence and the isospin dependence of other physical quantities, such as the proton and neutron single particle potentials and effective masses, are also studied. Due to the additional repulsion produced by the three-body force contribution, the proton and neutron single particle potentials are correspondingly enhanced as similar to the zero-temperature case.

An empirical investigation of the trends in the properties of the nonyrast $K^{\pi }=2_{\gamma }^{+}$ and $K^{\pi }=0_2^{+}$ bandhead configurations in nuclei that are related to one another through the addition or removal of $\alpha$-particle-like structures, reveals their complex and changing behavior in contrast to the smooth behavior of the yrast states. A systematic application of the pseudo-SU(3) model for such a sequence of deformed nuclei from the rare earth region leads to an accurate and unified description of not only yrast, but nonyrast collective bands. The onset of deformation as manifested through the position of the excited bandheads in the spectra is understood and interpreted by using a realistic model Hamiltonian in conjunction with a microscopic distribution of the eigenstates across allowed proton and neutron strong-coupled SU(3) configurations.

We study in cranked Nilsson plus random phase approximation the electric monopole $\left(E0\right)$, quadrupole $\left(E2\right)$, and magnetic dipole $\left(M1\right)$ responses in fast rotating nuclei undergoing backbending, more specifically ${}^{156}\mathrm{Dy}$ and ${}^{158}\mathrm{Er}$. Special attention is paid at the orbital $M1$ excitations known as scissors mode. We find that the overall strength of the orbital $M1$ transitions gets enhanced by more than a factor of 4 above the critical backbending region. We show that such a strength evolves with the rotational frequency in close correspondence with the nuclear moment of inertia. This link provides the main clue for understanding the physical origin of such an enhancement, which, if experimentally confirmed, would represent a distinctive feature of nuclei exhibiting backbending.

The decay of ${}^{154}\mathrm{Eu}\to {}^{154}\mathrm{Gd}$ has been studied by $\gamma$-ray singles and $\gamma -\gamma$ coincidence spectroscopy using an array of 20 Compton-suppressed $\mathrm{Ge}$ detectors. The primary goal of the work was to investigate the structure of ${}^{154}\mathrm{Gd}$ above $1\mathrm{MeV}$: The outcome is the removal of 11 levels from the previously adopted ${}^{154}\mathrm{Eu}$ decay scheme, the addition of 40 new $\gamma$-ray assignments, and upper limits set on 75 $\gamma$-ray transitions which had been previously assigned to the ${}^{154}\mathrm{Gd}$ level scheme. The current results, combined with data from other spectroscopic techniques, indicate that states which were previously interpreted as “two-phonon” excitations are either spurious or are shown to be of a different nature. These results provide a deeper understanding of the structure of ${}^{154}\mathrm{Gd}$ and the $N=90$ isotones.

Fission fragment angular distributions have been measured for the systems ${}^{11}\mathrm{B}+{}^{235}\mathrm{U}$ and ${}^{14}\mathrm{N}+{}^{232}\mathrm{Th}$, at sub and near-barrier energies. Complete and incomplete momentum transfer fission components have been separated around $90°\text{c.m.}$ for ${}^{14}\mathrm{N}+{}^{232}\mathrm{Th}$. The contribution of incomplete momentum transfer events is found to be about $8\%$ over the present energy range of investigation. In the ${}^{14}\mathrm{N}+{}^{232}\mathrm{Th}$ case, anisotropy data are found to be anomalous throughout the energy range, where as corresponding data for ${}^{11}\mathrm{B}+{}^{235}\mathrm{U}$ are found to be normal, with respect to the saddle-point statistical model predictions. The large ground state spin values of ${}^{11}\mathrm{B}$ and ${}^{235}\mathrm{U}$ are found to play a major role at the sub-barrier region in influencing the anisotropy values.

The $(d,p)$ stripping reaction has proved a useful tool for probing single particle aspects of nuclear structure. With the advent of beams of exotic nuclei there has been renewed interest in charged particle spectroscopy and $(d,p)$ stripping in particular as a means of investigating the structure of neutron-rich nuclei via reactions in inverse kinematics. The distorted wave Born approximation was shown to be inappropriate for the analysis of $(d,p)$ reactions some 30 years ago, due to the importance of the deuteron breakup channel. While the simple adiabatic model has been demonstrated to work rather well in this context, modern computing facilities enable a more realistic treatment of the deuteron breakup process via the continuum discretized coupled channels procedure to be included in $(d,p)$ calculations. In this work we present a comprehensive analysis method for $(d,p)$ reactions using CDCC to model deuteron breakup and the Reid soft-core nucleon-nucleon potential to calculate the deuteron internal wave function. The model is tested against ${}^{12}\mathrm{C}(d,p)$ data at incident deuteron energies of 15 and $30\mathrm{MeV}$ where all the necessary ancillary data are available. It is then applied to the ${}^{10}\mathrm{Be}(d,p)$ reaction at 12 and $25\mathrm{MeV}$ where only the transfer cross section data are available.

The $T_{20}$ analyzing powers have been measured for the ${}^{120}\mathrm{Sn}\left({}^7\mathrm{Li},{}^8\mathrm{Be}\to 2\alpha \right){}^{119}\mathrm{In}$ and ${}^{120}\mathrm{Sn}\left({}^7\mathrm{Li},{}^6\mathrm{Li}^{*}\to \alpha +d\right){}^{121}\mathrm{Sn}$ transfer breakup reactions, using a $70\mathrm{MeV}$ beam. The data exhibit excellent agreement with the results of coupled reaction channels calculations, providing an important test of these calculations when applied to the transfer breakup reaction mechanism.

The $\gamma +D\to \mathrm{\Lambda }+{\mathrm{\Theta }}^{+}$ and $\gamma +D\to \mathrm{\Sigma }+{\mathrm{\Theta }}^{+}$ reactions can be used to determine the width of ${\mathrm{\Theta }}^{+}$ almost model independently. We calculate the differential cross sections of the $\gamma +D\to \mathrm{\Lambda }+{\mathrm{\Theta }}^{+}$, $\gamma +D\to \mathrm{\Sigma }+{\mathrm{\Theta }}^{+}$ and relevant background reactions in the photon energy range $1.2⩽E_{\gamma }⩽2.6\mathrm{GeV}$. We determine the most favorable kinematic conditions and observables for the experimental studies of ${\mathrm{\Theta }}^{+}$ in the considered processes. We argue that a comparison of the $\gamma +D\to \mathrm{\Lambda }+{\mathrm{\Theta }}^{+}$ and $\gamma +D\to \mathrm{\Sigma }+{\mathrm{\Theta }}^{+}$ cross sections should unambiguously determine isospin of ${\mathrm{\Theta }}^{+}$.

We study the properties of the $\kappa$ meson in the nuclear medium, starting from a chiral unitary model of $S$-wave, $I=1∕2K\pi$ scattering, which describes the elastic $K\pi$ phase shifts and generates a pole in the amplitude. Medium effects are considered by including pion and kaon self-energies. We explore the changes in the $\kappa$ pole position and in the $K\pi$ scattering amplitude at finite density, with two different models for the kaon self-energy.

We have given an explanation for the pseudorapidity distribution of charged particles produced in $d+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ [the maximum relativistic heavy ion collider (RHIC) energy]. A simple cylinder model is used in this paper which contains four components: leading projectile protons, leading target protons, cascade collisions in the gold spectator, and a cylinder. The model gives a good description for the experimental data obtained with the PHOBOS detector at RHIC. The high stage and high peak in the gold fragmentation region of the pseudorapidity distribution are contributed by the leading gold protons and the cascade collisions in the gold spectator, respectively.

A core-excited $I^{\pi }=\left({12}^{+}\right)$ spin-gap isomer was identified in ${}^{98}\mathrm{Cd}$ in an experiment at EUROBALL IV. It was found to feed the known $I^{\pi }=\left(8^{+}\right)$ seniority isomer by an $E4$ transition. Half-lives of $T_{1∕2}=0.23$$\left(\genfrac{}{}{0ex}{}{+4}{-3}\right)\mu \mathrm{s}$ and 0.17$\left(\genfrac{}{}{0ex}{}{+6}{-4}\right)\mu \mathrm{s}$ were measured for the two states at $E_x=6635\mathrm{keV}$ and $2428\mathrm{keV}$, respectively. From the excitation energy of the core-excited isomer a ${}^{100}\mathrm{Sn}$ shell gap of $6.46\left(15\right)\mathrm{MeV}$ is inferred. The measured $E4$ and $E2$ strengths, ${}^{100}\mathrm{Sn}$ core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An $E2$ polarization charge for protons of $\delta e_{\pi }<0.4e$ is found, which corresponds to the empirical value $\delta e_{\pi }=0.45\left(\genfrac{}{}{0ex}{}{+20}{-25}\right)e$ in the pure proton hole valence space.