The structure of the $\Delta \Delta$ dibaryon is studied in terms of the chiral SU(3) quark model. The ground state energy of $\Delta \Delta$ dibaryon is evaluated by considering both the $\Delta \Delta$ and $\mathrm{CC}$ (hidden color) channels. The parameter-dependence of the $\Delta \Delta$ dibaryon mass is also investigated. It is shown that the resultant mass of the $\Delta \Delta$ dibaryon is lower than the threshold of the $\Delta \Delta$ channel but still higher than that of the $\Delta N\pi$ channel.

The yrast spectra, quadrupole deformation parameter $\left({\beta }_2\right),$ occupation probabilities, intrinsic static quadrupole moments, and $B\left(E2\mathrm{}\right)\mathrm{}$ transition probabilities are calculated for ${}^{114,116}\mathrm{Cd}$ isotopes by carrying out cranked-Hartree-Bogoliubov calculations. These calculations have been performed by employing a quadrupole–quadrupole-plus-pairing model of residual interaction operating in a reasonably large valence space outside the ${}^{76}\mathrm{Sr}$ core. Our calculations show that the systematics of low-lying levels in ${}^{114,116}\mathrm{Cd}$ depend upon the simultaneous increase in the occupation probabilities of the ${(d}_{5/2}{)}_{\nu }$ and ${(h}_{11/2}{)}_{\nu }$ orbits and also on the subshell closure of the ${(p}_{1/2}{)}_{\pi },$ ${(p}_{1/2}{)}_{\nu },$ and ${(g}_{9/2}{)}_{\nu }$ orbits. It turns out that the vibrational character of the Cd isotopes, in general, is due to the nonpolarizability of the $Z=40\mathrm{}$ and $N=50\mathrm{}$ core.

The possible contribution of two-photon exchange to electron deuteron elastic scattering at relatively high momentum transfer is discussed. This study was motivated by the high precision data recently obtained at the Jefferson Laboratory. Using general arguments, based on crossing symmetry for the processes $e^{-}+\overrightarrow{h}{e}^{-}+h$ and $e^{+}{+e}^{-}\to h+\overline{h},$ we find a parametrization for the angular dependence of the interference between the one- and two-photon exchanges in the differential cross section for elastic $\mathrm{ed}$ scattering in terms of a new kinematical variable and compare our findings to the recent data.

The doubly odd nucleus ${}^{170}\mathrm{Lu}$ has been studied using the ${}^{164}\mathrm{Dy}{(}^{11}\mathrm{B},5\mathrm{n})$ reaction at 63 MeV bombarding energy. A near yrast level scheme was constructed comprising 11 rotational bands. Among them, the $\tilde{\pi }{\mathrm{h}}_{9/2}\otimes \tilde{\nu }{\mathrm{i}}_{13/2}$ staggered semidecoupled structure has been established up to $I=30\mathrm{}ħ.$ The doubly decoupled band $\tilde{\pi }{\mathrm{h}}_{9/2}\otimes \tilde{\nu }{\frac{1}{2}}^{-}\left[521\right]$ and a Newby shifted $K=0\mathrm{}$ band were also found. A set of three bands resembles a band structure present in the neighboring odd-$A$ isotopes. One of these shows a striking similarity in transition energies to the $\tilde{\pi }{7/2}^{+}\left[404\right]$ band in ${}^{171}\mathrm{Lu}$ and hence this pair has been cataloged as twin bands. However, their extracted moments of inertia appear to be very different and therefore they cannot be considered identical bands in the usual sense.

Energy levels, dynamic moments of inertia of the superdeformed bands of ${}^{191,193}\mathrm{Hg}$ are studied by incorporating fermion degrees of freedom with the superdeformed interacting boson model. Except for the cases with band crossing, it is found that the single-fermion orbital dominance is sufficient for describing most of the superdeformed bands. The energy levels can be reproduced quite well. The dynamic moments of inertia can be reproduced reasonably well for most of the bands. However, the staggering of the moment of inertia observed in some superdeformed bands cannot be reproduced in the model. The general features of the wave functions are discussed.

High-spin states in ${}^{170}\mathrm{Ta}$ have been studied via ${}^{159}{\mathrm{T}\mathrm{b}(}^{16}\mathrm{O},5n\gamma {)}^{170}\mathrm{Ta}$ reaction through excitation functions, K x-γ, and $\gamma -\gamma -t$ coincidence measurements. Three rotational bands have been identified which consist of two strongly coupled bands and a semidecoupled one. The quasiparticle configurations of these bands and the interpretation of experimental results are discussed based on the existing knowledge of neighboring odd-mass and odd-odd nuclei and in the framework of the cranked-shell model. Low-spin signature inversion in the $\pi {9/2}^{-}\left[514\right]\otimes \nu {5/2}^{+}\left[642\right]$ and $\pi {1/2}^{-}\left[541\right]\otimes \nu {5/2}^{+}\left[642\right]$ bands are discussed. A delay (reduction) of the band-crossing frequency is observed in the $\pi {1/2}^{-}\left[541\right]\otimes \nu {5/2}^{+}\left[642\right]$ $\left(\pi {5/2}^{+}\right[402]\otimes \nu {5/2}^{+}[642\left]\right)$ band. This configuration-dependent crossing frequency is discussed in comparison with the AB crossing frequencies in the related bands of neighboring odd-Z isotopes.

A technique for the direct treatment of asymptotic binary channels in three-body systems with bound subsystems is developed in the framework of the hyperspherical harmonic (HH) method. The method is tested on the well-studied ${}^6\mathrm{Li}$ nucleus. Comparison with “pure” HH calculations shows faster convergence of the binding energy and larger matter radii. The model problem “${}^6\mathrm{Li}$” with a very loosely bound deuteron is considered and the result demonstrates the efficiency of the method in this case. The low-lying three-cluster states in ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ spectra are studied; various observables for such states are calculated in a three-body $\alpha {+}^3\mathrm{H}{(}^3\mathrm{He})+N$ model.

We present a calculation of $e^{+}{e}^{-}$ production in $\gamma A$ reactions at MAMI and TJNAF energies within a semiclassical Boltzmann-Uehling-Uhlenbeck transport model. Dilepton invariant mass spectra for γC, γCa, and γPb are calculated at 0.8, 1.5, and 2.2 GeV. We focus on observable effects of medium modifications of the $\rho$ and $\omega$ mesons. The in-medium widths of these mesons are taken into account in a dynamical, consistent way. We discuss the transport theoretical treatment of broad resonances.

Charged kaon production has been measured in Si+Al and Si+Au collisions at $14.6A\hspace{0.5em}\mathrm{GeV}/c$, and Au+Au collisions at $11.1A\hspace{0.5em}\mathrm{GeV}/c$ by Experiments 859 and 866 (the E-802 Collaboration) at the BNL AGS. Invariant transverse mass spectra and rapidity distributions for both $K^{+}$ and $K^{-}$ are presented. The centrality dependence of rapidity-integrated kaon yields is studied. Strangeness enhancement is observed as an increase in the slope of the kaon yield with the total number of participants as well as the yield per participant. The enhancement starts with peripheral Si+Al and Si+Au collisions (relative to $N+N)$ and appears to saturate for a moderate number of participating nucleons in Si+Au collisions. It is also observed to increase slowly with centrality in Au+Au collisions, to a level in the most central Au+Au collisions that is greater than that found in central $\mathrm{Si}+A$ collisions. The enhancement factors for $K^{+}$ production are $3.0\pm 0.2\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)$ and $4.0\pm 0.3\left(\mathrm{stat}\right)\pm 0.5\left(\mathrm{syst}\right)$, respectively, for the most central 7% Si+Au collisions and the most central 4% Au+Au collisions relative to $N+N$ at the correponding beam energy.

We evaluated box and crossed-box two-pion exchange diagrams. We found that form factors can induce contributions that violate the unitary cut requirement, and that the sum of subtracted and crossed-box amplitudes depends crucially on the meson-nucleon vertex functions. With form factors preserving the unitarity condition, this sum can be made, at low energies, of the order of one heavy boson exchange, supporting the idea that it may be effectively represented by such types of terms.

Triggered by experimental evidence formerly obtained for Zr and Mo isotopes, a survey of the literature in the $A\sim 100$ region was undertaken and revealed that $5_1^{-}$ states exist in even-even nuclei throughout the $40<~Z<~50$ region. They appear at an almost constant excitation energy of $(2.4\mathrm{}\pm 0.2)$ MeV and have, where studied in inelastic scattering, characteristics of one-step collective excitations. Angular distributions for ${}^{94,98}\mathrm{Mo}{(d,d}^{\prime })$ are presented for states at 2.611 MeV in ${}^{94}\mathrm{Mo}$ and 2.622 MeV in ${}^{98}\mathrm{Mo}$ and ${\beta }_5$ values were extracted. The ${\beta }_5$ value for ${}^{94}\mathrm{Mo}$ is new in the literature and was obtained consistently for two incident energies. The ${\beta }_5$ value for ${}^{98}\mathrm{Mo}$ is higher than a former result, where a two-phonon interpretation was considered.

Mass-energy distributions of the ${}^{220}\mathrm{Ra}$ fission fragments produced in the ${}^{12}\mathrm{C}{+}^{208}\mathrm{Pb}$ reaction at projectile energies higher and deep below the Coulomb barrier have been measured using a two-arm time-of-flight spectrometer CORSET. It has been shown that an asymmetric component appears at the sides of the prevailing symmetric fission with a cooling of the compound nucleus. The component consists of two standard modes with average masses of $\simeq 132$ and $\simeq 139.$ A three-component structure has also been observed in the total kinetic energy distributions in the range of asymmetric fission fragment masses.

We discuss the nucleon to higher-spin N- and $\Delta$-resonance transitions by pions and photons. The higher-spin baryons are described by Rarita-Schwinger fields and, as we argue, this imposes a stringent consistency requirement on the form of the couplings. Popular $\pi N\Delta$ and $\gamma N\Delta$ couplings are inconsistent from this point of view. We construct examples of consistent interactions with the same nonrelativistic limit as the conventional ones.

The potential for using deep inelastic reactions to populate high-spin states in neutron-rich nuclei is studied in a series of experiments using GAMMASPHERE for $\gamma$-ray detection and a silicon strip detector for measuring the angles of projectilelike and targetlike fragments. In three experiments 61 new transitions up to a maximum spin of 22$ħ$ in 12 neutron-rich rare-earth nuclei were found. We observe that $\gamma$-ray yields as a function of spin are flatter for all neutron transfer products than for inelastic excitation of either the projectile or target nucleus. Calculations are presented which indicate that this difference cannot be accounted for by quasielastic processes, but more likely are the result of larger energy loss processes, such as deep inelastic reactions.

Positron and electron quasielastic cross sections on ${}^{12}\mathrm{C}$ and ${}^{208}\mathrm{Pb}$ were measured at the Saclay linear accelerator (ALS) to test Coulomb corrections to the plane-wave Born approximation. The positron and electron response functions at the same effective kinematics were found to be equal within a 3% experimental uncertainty, which allows us to discriminate between different theoretical models of Coulomb distortions. Our result strongly supports the effective momentum approximation, even for nuclei as heavy as ${}^{208}\mathrm{Pb}$.

The ${}^{12}\mathrm{C}(\gamma ,pd)$ reaction has been studied for photon energies between 150 and 400 MeV using the Glasgow photon tagging spectrometer and plastic scintillator detectors at the Mainz MAMI electron accelerator. The overall energy resolution was $\sim 6$ MeV, sufficient to determine the initial shells of the emitted nucleons. The energy dependence of the cross section and the missing energy and recoil momentum spectra indicate that, for low residual excitation, the reaction proceeds through interaction with the three detected nucleons in a similar manner to the ${}^3\mathrm{He}(\gamma ,pd)$ reaction while the rest of the nucleus acts as a spectator.

The validity of the method of continuum discretized coupled channels (CDCC) is numerically tested and confirmed for a realistic example of ${d+}^{58}\mathrm{Ni}$ scattering at 80 MeV. Elastic and breakup S-matrix elements, calculated with the CDCC method, numerically converge as the model space is extended, viz., the internal angular momentum of the proton-neutron pair and the matching radius are increased. Two methods of discretization, the average method and midpoint method, of the continuum of the internal linear momentum of the $p-n$ pair are tested and found to yield the same results.

The instability of a Fermi-liquid drop with respect to bulk density distortions is considered. It is shown that the presence of the surface strongly reduces the growth rate of the bulk instability of the finite Fermi-liquid drop because of the anomalous dispersion term in the dispersion relation. The instability growth rate is reduced due to the Fermi-surface distortions and the relaxation processes. The dependence of the bulk instability on the multipolarity of the particle density fluctuations is demonstrated for two nuclei ${}^{40}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$. It is shown that the formation of the decay modes (fission or multifragmentation) of an unstable Fermi-liquid drop depends on the location of the radial wave number q on the slopes of the instability growth rate $\Gamma \mathrm{}\left(q\right)\mathrm{}$ and is different for both nuclei ${}^{40}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$.

A coplanar three body cluster model (two deformed fragments and an α particle) similar to the model used for the description of cold binary fission was employed for the description of cold (neutronless) α accompanied fission of ${}^{252}\mathrm{Cf}.$ No preformation factors were considered. The three body potential was computed with the help of a double folding potential generated by the M3Y-NN effective interaction and realistic fragment ground state deformations. From the minimum action principle, the α particle trajectory equations, the corresponding ternary barriers, and an approximate WKB expression for the barrier penetrability are obtained. The relative cold ternary yields were calculated as the ratio of the penetrability of a given ternary fragmentation and the sum of the penetrabilities of all possible cold ternary fragmentations. Different scenarios were considered depending on the trajectories of the fragments. It was shown that two regions of cold fragmentation exist, a deformed one corresponding to large fragment deformations and a spherical one around ${}^{132}\mathrm{Sn},$ similarly to the case of the cold binary fission of ${}^{252}\mathrm{Cf}.$ We have shown that for the scenario corresponding to the Lagrange point, where all forces acting on the α particle are in equilibrium, the cold α ternary yields of ${}^{252}\mathrm{Cf}$ are strongly correlated with the cold binary yields of the daughter nucleus ${}^{248}\mathrm{Cm}$ into the same heavy fragments. For all other scenarios only the spherical splittings are favored. We concluded that due to the present available experimental data on cold α ternary yields only the Lagrange scenario could describe the cold α ternary fission of ${}^{252}\mathrm{Cf}.$

We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission, and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments, and pions, produced electromagnetically, are also calculated. These results provide important information for designing large-rapidity detectors and zero-degree calorimeters at the relativistic heavy-ion colliders. The electromagnetic dissociation of nuclei imposes some constraints on the investigation of exotic particle production in $\gamma \gamma$ fusion reactions.