The coupled $\eta N$, $\pi N$, $\gamma N$, $\pi \pi N$ system is described by a $K$-matrix method. The parameters in this model are adjusted to get an optimal fit to $\pi N\to \pi N$, $\pi N\to \eta N$, $\gamma N\to \pi N$, and $\gamma N\to \eta N$ data in an energy range of about 100 MeV or so each side of the $\eta$ threshold. Compared with our earlier analysis, we now utilize recent Crystal Ball data. However, the outcome confirms our previous result that the $\eta$-nucleon scattering length $a$ is large with a value of $\mathrm{0.91(6)}+i0.27(2)\mathrm{fm}$.

Polarization-transfer components for ${}^4\mathrm{He}$$(\overrightarrow{e},e^{\text{'}}\overrightarrow{p})$${}^3\mathrm{H}$ and ${}^{16}\mathrm{O}$$(\overrightarrow{e},e^{\text{'}}\overrightarrow{p})$${}^{15}\mathrm{N}$ are computed within the relativistic multiple-scattering Glauber approximation (RMSGA). The RMSGA framework adopts relativistic single-particle wave functions and electron-nucleon couplings. The predictions closely match those of a relativistic plane-wave model indicating the smallness of the final-state interactions for polarization-transfer components. Also short-range correlations play a modest role for the studied observables, as long as small proton missing momenta are probed in quasielastic kinematics. The predictions with free and various parametrizations for the medium-modified electromagnetic form factors are compared to the world data.

The fully consistent relativistic proton-neutron quasiparticle random phase approximation (PN-RQRPA) is employed in the calculation of β-decay half-lives of neutron-rich nuclei in the $N\approx 50$ and $N\approx 82$ regions. A new density-dependent effective interaction, with an enhanced value of the nucleon effective mass, is used in relativistic Hartree-Bogoliubov calculation of nuclear ground states and in the particle-hole channel of the PN-RQRPA. The finite range Gogny D1S interaction is employed in the $T=1$ pairing channel, and the model also includes a proton-neutron particle-particle interaction. The theoretical half-lives reproduce the experimental data for the Fe, Zn, Cd, and Te isotopic chains but overestimate the lifetimes of Ni isotopes and predict a stable ${}^{132}\mathrm{Sn}$.

We present a novel approach to the density-dependent mean field and the spin-orbit interaction of a $\Lambda$ hyperon in a nuclear many-body system, based on flavor-SU(3) in-medium chiral perturbation theory. The leading long-range $\Lambda N$ interaction arises from kaon exchange and from two-pion exchange with a $\Sigma$ hyperon in the intermediate state. The empirical $\Lambda$-nucleus potential depth of about $-28\mathrm{MeV}$ is well reproduced with a single cutoff scale, $\overline{\Lambda }=0.7\mathrm{GeV}$, effectively representing all short-distance (high-momentum) dynamics not resolved at scales characteristic of the nuclear Fermi momentum. This value of $\stackrel{\hspace{1em}}{\Lambda }$ is remarkably consistent with the one required to reproduce the empirical saturation point of isospin-symmetric nuclear matter in the same framework. The smallness of the $\Lambda$-nuclear spin-orbit interaction finds a natural (yet novel) explanation in terms of an almost complete cancellation between short-range contributions (properly rescaled from the known nucleonic spin-orbit coupling strength) and long-range terms generated by iterated one pion exchange with intermediate $\Sigma$ hyperons. The small $\Sigma \Lambda$-mass difference figures prominently in this context.

In the present work short-range correlations are introduced for the first time in a relativistic approach to the equation of state of the infinite nuclear matter in the framework of the Hartree-Fock approximation using an effective Hamiltonian derived from the $\sigma \text{−}\omega$ Walecka model. The unitary correlation method is used to introduce short-range correlations. The effect of the correlations in the ground state properties of the nuclear matter is discussed.

Lifetimes of some high-spin states in the negative parity magnetic dipole band in ${}^{112}\mathrm{Sb}$ were determined using the Doppler-shift attenuation method. The deduced $M1$ transition rates show a small decrease with increasing spin. This decrease is reasonably accounted for within the framework of the tilted axis cranking (TAC) model. There also appears to be a considerable contribution from collective rotation. This is the first indication of such behavior in the $A\approx 110$ mass region, determined through lifetime measurements. The TAC calculations based on a $\pi g{{}_{9/2}}^{-1}\otimes \nu h_{11/2}$ configuration reproduce the magnetic dipole band.

In standard statistical approaches on nuclear disassembly, the fragmentation pattern is decided at the “freeze-out” volume, generally taken to be 3–8 times the normal nuclear volume. In this communication, we show that the dynamics of the initially produced fragments may allow pairs of fragments to come well within the nuclear force range resulting in possible recombination in the exit channel. The fused complex may undergo further fragmentation if sufficiently excited. This alters the fragmentation pattern and the associated physical observables considerably. The ambiguity so found calls for critical reanalysis of the different statistical approaches to nuclear multifragmentation.

We study the possible signals of a pion string associated with the QCD chiral phase transition in LHC Pb-Pb collision at energy $\sqrt{s}=5.5\text{TeV}$. In terms of the Kibble-Zurek mechanism we discuss the production and evolution of the pion string. The pion string is not topologically stable; it decays into neutral pions and sigma mesons that in turn decay into pions. Our results show that all the neutral pions from the pion string are distributed at the low momentum and the ratio of neutral to charged pions from the pion string violates the isospin symmetry. For the momentum spectra of the total pions, the signal from the sigma particle decay from the pion string will be affected by the large decay width of the sigma significantly.

Understanding the properties of ${}^{19}\mathrm{F}$ levels in the range $E_x=6.4-7.5\text{MeV}$ is important for constraining the contributions of ${}^{19}\mathrm{Ne}$ levels to the ${}^{18}\mathrm{F}$($p,\alpha$)${}^{15}\mathrm{O}$ and ${}^{18}\mathrm{F}$($p,\gamma$)${}^{19}\mathrm{Ne}$ thermonuclear reaction rates. We have reanalyzed ${}^{15}\mathrm{N}$($\alpha ,\alpha$)${}^{15}\mathrm{N}$ data from H. Smotrich et al. [Phys. Rev. 122, 232 (1961)] to determine properties of ${}^{19}\mathrm{F}$ levels in this energy range. We find the energies and widths of broad levels to be different than previously reported and have set upper limits on the widths of postulated $3/2^{+}$ resonances, analogs of which are important for the ${}^{18}\mathrm{F}+p$ rates.

The low-lying orbital magnetic dipole strength in even-even nuclei is discussed using a sum-rule approach. It is shown that both the mean excitation energies as well as the summed excitation strengths from the experiment can be described well in heavy nuclei if the moments of inertia and the $g$ factors are substituted by the parameters of the ground-state rotational bands. The influence of the high-lying scissors mode is taken into account explicitly, leading to a successful description of the low-lying mode in heavy deformed nuclei with no free parameters. A quantitative estimate of the gross features of the high-lying mode is deduced. The application of the sum-rule approach to medium-mass nuclei is presented, and the discrepancies with the experimental data are discussed.

We study ground-state properties of the doubly magic nuclei ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$ employing the Goldstone expansion and using as input four different high-quality nucleon-nucleon (NN) potentials. The short-range repulsion of these potentials is renormalized by constructing a smooth low-momentum potential $V_{\mathrm{low}\text{−}k}$. This is used directly in a Hartree-Fock approach, and corrections up to third order in the Goldstone expansion are evaluated. Comparison of the results shows that they are only slightly dependent on the choice of the NN potential.

Differential cross sections for the quasielastic scattering of a 25 MeV/nucleon ${}^6\mathrm{He}$ on a ${}^9\mathrm{Be}$ target have been measured. A double-folding model approach has been applied to generate the real part of the optical potential. An optical model analysis has been carried out to study the potential parameters by optimally fitting the experimental angular distribution. In the context of the coupled-channel calculation the contribution of the inelastic channels to the experimental data has been found to be small. The effect of the unstable property of the ${}^6\mathrm{He}$ nucleus is discussed.

The backbending phenomena observed in Ce isotopes, ${}^{132,134,136}\mathrm{Ce}$ are investigated in terms of a pair-truncated shell model, a fully microscopic theory that conserves the nucleon number and the total spin. The model reproduces the backbending phenomena quite well, where the experimental bending point of ${}^{132}\mathrm{Ce}$ is spin 12 and those of ${}^{134}\mathrm{Ce}$ and ${}^{136}\mathrm{Ce}$ are spin 10. In addition to high spin states, the theory provides a successful description of energy levels for low-lying collective states as well as those electromagnetic properties, such as $B(E2)$ branching ratios and $g$ factors.

The half-lives of different spherical proton emitters are calculated. The preformed cluster model modified into a unified fission model of Gupta and collaborators with the effects of Coulomb repulsion, nuclear attraction due to proximity potential, and rotational energy due to angular momentum is used for the calculations. This includes the study of observed ground and isomeric state proton emitters of 26 proton-rich nuclei. The results are compared with experimental results and other theoretical calculations. The calculated results are in fair agreement with experimental values. It is evident from some experiments that $\alpha$ decay is a competing mode of branching for proton decay. Hence, the half-lives of $\alpha$ decay from these proton emitters are also presented for $s$ waves.

Systematic analysis of deformations in neutron-rich $N=14$ isotones was done based on the method of antisymmetrized molecular dynamics. The property of the shape coexistence in ${}^{28}\mathrm{Si}$, which is known to have the oblate ground state and the prolate excited states, was successfully described. The results suggest that the shape coexistence may occur also in neutron-rich $N=14$ nuclei as well as ${}^{28}\mathrm{Si}$. It was found that the oblate neutron shapes are favored because of the spin-orbit force in most of $N=14$ isotones. $Q$ moments and $E2$ transition strengths in the neutron-rich nuclei were discussed in relation to the intrinsic deformations, and a possible difference between the proton and neutron deformations in ${}^{24}\mathrm{Ne}$ was proposed.

Independent isomeric yield ratios (IYR) of ${}^{128}\mathrm{Sb}$, ${}^{130}\mathrm{Sb}$, ${}^{132}\mathrm{Sb}$, ${}^{131}\mathrm{Te}$, ${}^{133}\mathrm{Te}$, ${}^{132}\mathrm{I}$, ${}^{134}\mathrm{I}$, ${}^{136}\mathrm{I}$, ${}^{135}\mathrm{Xe}$, and ${}^{138}\mathrm{Cs}$ have been determined in fast neutron induced fission of ${}^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, ${}^{240}\mathrm{Pu}$, and ${}^{244}\mathrm{Cm}$ as well as in thermal neutron induced fission of ${}^{232}\mathrm{U}$ and ${}^{238}\mathrm{Pu}$ using radiochemical and offline $\gamma$-ray spectrometric techniques. From the IYR, fragment angular momenta ($J_{\mathrm{rms}}$) have been deduced using a spin-dependent statistical model analysis. These data along with the literature data for ${{}^{230}\mathrm{Th}}^{\ast }$, ${{}^{234}\mathrm{U}}^{\ast }$, ${{}^{236}\mathrm{U}}^{\ast }$, ${{}^{240}\mathrm{Pu}}^{\ast }$, ${{}^{242}\mathrm{Pu}}^{\ast }$, ${}^{244}\mathrm{Cm}$(SF), ${{}^{246}\mathrm{Cm}}^{\ast }$, ${{}^{250}\mathrm{Cf}}^{\ast }$, and ${}^{252}\mathrm{Cf}$(SF) for fifteen even-$Z$ fissioning systems show the following important features: (i) The $J_{\mathrm{rms}}$ of the odd-$Z$ fission products are higher than those of the even-$Z$ fission products, indicating the odd-even effect. For both the odd-$Z$ and even-$Z$ fission products, the $J_{\mathrm{rms}}$ increase with $Z_F^2/A_F$. (ii) The $J_{\mathrm{rms}}$ of fragments with spherical 50-$p$ and 82-$n$ shells are lower compared to those of fragments outside the spherical shell, indicating the effect of shell closure proximity. (iii) The $J_{\mathrm{rms}}$ of the fission products increase with mass number in spite of fluctuations in shell closure proximity and odd-even effects but do not show any correlation with the neutron emission curve. (iv) In all fifteen even-$Z$ fissioning systems from Th to Cf, the yield-weighted $J_{\mathrm{rms}}$ values show an anticorrelation with the elemental yields. (v) The odd-even fluctuation on $J_{\mathrm{rms}}$ does not change drastically from Th to Cf, unlike the proton odd-even effect (${\delta }_p$) which decreases significantly with the increase of Coulomb parameter ($Z_F^2/A_F^{1/3}$).

The cluster radioactivity is treated under the assumption that the light clusters are produced by a collective motion of the nuclear system in the charge asymmetry coordinate with further penetration through the Coulomb barrier. The known experimental data on cluster radioactivity are described. The half-lives of cluster emission of neutron-deficient actinides and medium-mass nuclei are predicted.

Low-energy excited states of ${}^{208}\mathrm{Ra}$ were investigated using the ${}^{182}\mathrm{W}$(${}^{30}\mathrm{Si}$, 4n) reaction at the Wright Nuclear Structure Laboratory of Yale University. Fusion evaporation recoils were selected using the gas-filled spectrometer SASSYER. Delayed $\gamma$ rays, following isomeric decays, were detected at the focal plane of SASSYER with a small array of three clover Ge detectors. Transitions following a proposed $J^{\pi }=8^{+}$ isomer were observed, and the half-life was measured.

We describe a method of estimating cross sections for the synthesis of very heavy nuclei by the fusion of two lighter ones. The cross section is considered to be the product of three factors: the cross section for the projectile to overcome the Coulomb barrier, the probability that the resulting composite nucleus reaches the compound nucleus configuration by a shape fluctuation treated as a diffusion of probability in one dimension, and the probability that the excited compound nucleus survives fission. Semi-empirical formulas for the mean Coulomb barrier height and its distribution around the mean are constructed. After overcoming the Coulomb barrier the system is assumed to be injected into an “asymmetric fission valley” by a rapid growth of the neck between the target and projectile at approximately frozen asymmetry and elongation. Diffusion in the elongation coordinate in this valley can occasionally bring the system over the saddle separating the injection point from the compound nucleus configuration. This is the stage that accounts for the hindrance to fusion observed for very heavy reacting systems. The competition between deexcitation of the compound nucleus by neutron emission and fission is treated by standard methods, but an interesting insight allows one to predict in an elementary way the location of the maximum in the resulting excitation function. Adjusting one parameter in the theory causes the calculated peak cross sections to agree within about a factor of 2 or so with 12 measured or estimated values for “cold” one-neutron-out reactions where targets of ${}^{208}\mathrm{Pb}$ and ${}^{209}\mathrm{Bi}$ are bombarded with projectiles ranging from ${}^{48}\mathrm{Ca}$ to ${}^{70}\mathrm{Zn}$. The centroids of the excitation functions agree with theory to within 1 or 2 MeV for the six cases where they have been determined, and their widths are reproduced. “Hot” fusion reactions, where several neutrons are emitted, are not treated, except that a comparison is made between the hindrance factors in cold and hot reactions to make elements with atomic numbers 112 to 118. The calculated diffusive hindrances in the hot reactions are less unfavorable by 4 to 5 orders of magnitude.