We start from a low-energy effective field theory for interacting fermions on the lattice and expand in the hopping parameter to derive the nearest-neighbor interactions for a lattice gas model. In this model, the renormalization of couplings for different lattice spacings is inherited from the effective field theory, systematic errors can be estimated a priori, and the breakdown of the lattice gas model description at low temperatures can be understood quantitatively. We apply the lattice gas method to neutron matter and compare with results from a recent quantum simulation.

A recently introduced scheme for the renormalization of the Hartree-Fock-Bogoliubov equations in the case of zero-range pairing interaction is extended to the relativistic Hartree-Bogoliubov model. A density-dependent strength parameter of the zero-range pairing is adjusted in such a way that the renormalization procedure reproduces the empirical ${}^1{S}_0$ pairing gap in isospin-symmetric nuclear matter. The model is applied to the calculation of ground-state pairing properties of finite spherical nuclei.

Polarized Compton scattering on the deuteron is studied in nuclear effective field theory. A set of tensor structures is introduced to define 12 independent Compton amplitudes. The scalar and vector amplitudes are calculated up to next-to-next-to-leading order in low-energy power counting. Significant contribution to the vector amplitudes is found to come from the spin-orbit type of relativistic corrections. A double-helicity-dependent cross section ${\Delta }_{1}d\sigma /d\Omega =(d{\sigma }_{+1-1}-d{\sigma }_{+1+1})/2d\Omega$ is calculated to the same order, and the effect of the nucleon isoscalar spin-dependent polarizabilities is found to be smaller than the effect of isoscalar spin-independent ones. Contributions of spin-independent polarizabilities are investigated in various asymmetries, one of which has an effect as large as 12% (26%) at the center-of-mass photon energy 30 (50) MeV.

We investigate the effect of monopole and quadrupole modes on the elastic $\alpha \text{−}\alpha$ resonance structure of ${}^8\mathrm{Be}$. To this end, we make a fully microscopic coupled-channels calculation with three coupled channels, using the algebraic model. The continuum spectrum and wave functions are analyzed in terms of the individual channels to understand the nature of the resonances. It is shown that both monopole and quadrupole modes have a nonnegligible effect on the resonances in the $\alpha \text{−}\alpha$ continuum.

Isospin and density waves in asymmetric nuclear matter (ANM) are studied in the framework of relativistic mean-field hadron models. A semiclassical relativistic approach based on the Vlasov equation is applied to the study of infinite asymmetric nuclear matter. The isovector and isoscalar collective modes are determined for a wide range of densities as a function of isospin asymmetry and momentum transfer. The condition for the existence of each type of mode is referred. The instabilities of ANM, related to the liquid-gas phase transition, are investigated.

The anisotropy in the angular distribution of α particles from oriented ${}^{253,254}\mathrm{Es}$ and ${}^{255}\mathrm{Fm}$ nuclei, which are among the strongest deformed α emitters, was measured. Large α anisotropies have been observed for all three nuclei. The results are compared with calculations based on α-particle tunneling through a deformed Coulomb barrier.

We implement an effective operator formalism for general one- and two-body operators, obtaining results consistent with the no-core shell model (NCSM) wave functions. The Argonne V8’ nucleon-nucleon potential was used in order to obtain realistic wave functions for ${}^4\mathrm{He},{}^6\mathrm{Li}$, and ${}^{12}\mathrm{C}$. In the NCSM formalism, we compute electromagnetic properties using the two-body cluster approximation for the effective operators and obtain results which are sensitive to the range of the bare operator. To illuminate the dependence on the range, we employ a Gaussian two-body operator of variable range, finding weak renormalization of long range operators (e.g., quadrupole) in a fixed model space. This is understood in terms of the two-body cluster approximation which accounts mainly for short-range correlations. Consequently, short-range operators, such as the relative kinetic energy, will be well renormalized in the two-body cluster approximation.

The stable nucleus ${}^{174}\mathrm{Yb}$ has been studied using deep-inelastic reactions and time-correlated γ-ray spectroscopy. New intrinsic states assigned include a 370-ns isomer at 1765 keV, which we associate with a predicted $K^{\pi }=7^{-}$ two-quasineutron configuration. Analysis of the alignment and in-band properties of its rotational band, identified using time-correlated coincidences, allows characterization of the configuration. The properties of a newly identified rotational band built on the known 830-μs isomer at 1518 keV support the $6^{+}$, 2-quasineutron configuration assignment proposed previously. The $6^{+}$ band is fed by a four-quasiparticle, $K^{\pi }={14}^{+}$ isomer at 3699 keV and several higher multiquasiparticle states, including a six-quasiparticle isomer at 6147 keV with K$=$(22,23). The results are discussed in terms of the states predicted on the basis of multiquasiparticle calculations. The anomalously fast K-forbidden transition strengths from the ${14}^{+}$ isomer are attributed to either K mixing in the neutron configuration or to random mixing in the high-level-density region. The $7^{-}$ isomer decays are not abnormal, whereas the very hindered E2 transition from the $6^{+}$ isomer to the ground-state band remains unexplained.

Recent high precision experimental data for heavy-ion fusion reactions at sub-barrier energies systematically show that a surprisingly large surface diffuseness parameter for a Woods-Saxon potential is required in order to fit the data. We point out that experimental data for quasielastic scattering at backward angles also favor a similar large value of the surface diffuseness parameter. Consequently, a double folding approach with a short-range imaginary potential for the compound nucleus formation fails to reproduce the experimental excitation function of quasielastic scattering for the ${}^{16}\mathrm{O}+{}^{154}\mathrm{Sm}$ system at energies around the Coulomb barrier. We also show that the deviation of the ratio of the quasielastic to the Rutherford cross sections from unity at deep sub-barrier energies offers an unambiguous way to determine the value of the surface diffuseness parameter in the nucleus-nucleus potential.

The excitation function for the fusion-evaporation reaction ${}^{64}\mathrm{Ni}+{}^{100}\mathrm{Mo}$ has been measured down to a cross section of ∼5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep falloff of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at $E_s=120.6\mathrm{MeV}$, which corresponds to 90% of the reference energy $E_s^{\mathrm{ref}}$, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass $A=100\text{−}200$ is presented in order to explore a possible dependence of fusion hindrance on nuclear structure.

We develop a theoretical framework for calculation of high-$Q^2$ exclusive electrodisintegration of $A=3$ systems. The main result of this work is the calculation of the final state interaction of the struck energetic nucleon with recoil nucleons within the generalized eikonal approximation (GEA), which allows us to account for the finite and relatively large momenta of the bound nucleons in the nucleus. This approach makes it possible to study in a self-consistent way the short-range correlations in nuclei. This is because the GEA does not require a stationary condition for recoil nucleons as does the conventional Glauber approximation. As a result GEA treats explicitly the Fermi motion of recoil nucleons in the nucleus.

Based on the theoretical framework of a generalized eikonal approximation, we study the two-nucleon emission reactions in high $Q^2$ electrodisintegration of ${}^3\mathrm{He}$. Our main aim is to investigate those features of the reaction which can be unambiguously identified with the short-range properties of the ground state nuclear wave function. To evaluate the differential cross section, we work in the formalism of the decay function which characterizes the property of the ground state wave function as well as the decay properties of the final two-nucleon spectator system. Our main motivation here is to explore the accessibility of two- and three-nucleon short-range correlations in ${}^3\mathrm{He}$ as well as to isolate unambiguously single and double rescattering processes in the reaction dynamics. Our analysis also allowed us to identify new approaches for investigating the role of the practically unknown three-nucleon forces in the ground state wave function of ${}^3\mathrm{He}$.

Angular distribution of fission fragments have been measured for ${}^{19}\mathrm{F}+{}^{197}\mathrm{Au}$ reaction at bombarding energies from 91 to 110 MeV. Fission fragment angular distributions have been calculated by transition state model with the transmission coefficients obtained using the coupled-channels theory. The calculated angular anisotropies are in good agreement with the experimental anisotropies. The experimental fission cross sections have also been reproduced on the basis of the coupled-channels theory. The results of angular distribution measurement do not show any significant contribution from quasifission as was reported in the literature based on the measurement of evaporation residues and mass distribution.

A large number of new measurements with the activation technique were performed for $(n,2n)$ and neutron-induced $\Delta Z=1,2$ reaction cross sections on the stable molybdenum isotopes in the energy range from 13.5 to 21 MeV. First results were obtained for the ${}^{92}\mathrm{Mo}(n,2n){{}^{91}\mathrm{Mo}}^m,{}^{92}\mathrm{Mo}(n,\alpha ){{}^{89}\mathrm{Zr}}^m,{}^{94}\mathrm{Mo}$$(n,2n){{}^{93}\mathrm{Mo}}^m,{}^{95}\mathrm{Mo}(n,p){{}^{95}\mathrm{Nb}}^m,{}^{96}\mathrm{Mo}(n,p){}^{96}\mathrm{Nb},{}^{96}\mathrm{Mo}(n,x)$${{}^{95}\mathrm{Nb}}^m$, ${}^{97}\mathrm{Mo}$$(n,p)$${}^{97}\mathrm{Nb}$, ${}^{97}\mathrm{Mo}$$(n,p)$${{}^{97}\mathrm{Nb}}^m$, ${}^{97}\mathrm{Mo}$$(n,x)$${}^{96}\mathrm{Nb}$, ${}^{98}\mathrm{Mo}$$(n,p)$${{}^{98}\mathrm{Nb}}^m$, ${}^{98}\mathrm{Mo}$$(n,x)$${}^{97}\mathrm{Nb}$, ${}^{98}\mathrm{Mo}$$(n,x)$${{}^{97}\mathrm{Nb}}^m$, and ${}^{100}\mathrm{Mo}$$(n,\alpha )$${}^{97}\mathrm{Zr}$ reactions, above 16 MeV. A significant number of high-accuracy 14 MeV measurements were performed which are in good agreement with the measurements above 16 MeV for reactions studied in both energy ranges. The rather complete database for the molybdenum isotopes was analyzed with two different sets of consistent model calculations: a local and a global approach. The global approach (a blind calculation with the TALYS code) provides a good overall description of the dominant reaction channels, although the $(n,\alpha )$ reactions for the heavy isotopes are overpredicted. The local approach (an adjusted calculation with the STAPRE-H code) describes the shapes and magnitudes of the excitation functions well from the reaction thresholds up to 21 MeV using a consistent parameter set, which was optimized based on all experimental information for the nuclei at hand and their immediate neighbors. The agreement between experimental and calculated data is, in general, good both at the maxima and at the tails of the excitation functions, and both for total activation cross sections of a particular channel and for cross sections leading to isomers, showing the viability of the level densities, the optical models, and the γ widths. Comparison of the two model calculations with the data indicates the relevance of an appropriate treatment for preequilibrium (PE) α-particle emission for the description of the data above 14 MeV. Comparison between the model calculations shows largely different PE deuteron emission contributions to the total $(\Delta Z=1,\Delta A=1)$ cross sections with an additional marked difference in energy dependence. This suggests that emission spectra around 20 MeV are required to establish the magnitude of the PE deuteron emission contribution to this process. New γ-ray strength functions were established by verification against average $(n,\gamma )$ data and were demonstrated to give good agreement with the measured isomer production cross sections.

We have studied the widths of the rapidity distributions of particles produced in nucleus-nucleus collisions at various center of mass energies and as a function of centrality at CERN Super Proton Synchrotron (SPS) energies. We show that the width of the rapidity distribution is sensitive to longitudinal flow, velocity of sound in the medium, and rescattering of particles. We explore the possibility of distinguishing the initial hard scattering regime from final state effects by studying the variation in the width of the rapidity distribution of the particles with centrality for various $p_T$ values.

The probability distributions for charged particle numbers and their densities are derived in statistical ensembles with conservation laws. It is shown that if this limit is properly taken, then the canonical and grand canonical ensembles are equivalent. This equivalence is proven on the most general probability distribution level.

To search for the $2_{1,\mathrm{ms}}^{+}$ state of ${}^{148}\mathrm{Sm}$, we studied the ${}^{148}\mathrm{Sm}(\gamma ,{\gamma }^{\text{'}})$ photon scattering reaction at the Stuttgart Dynamitron accelerator using bremsstrahlung with an endpoint energy of 3.2 MeV. Nuclear resonance fluorescence from eleven excited states, including three $2^{+}$ states, between 1.4 and 3.1 MeV has been observed. The data allow the identification of the $2_5^{+}$ state at 2146 keV as the $2_{1,\mathrm{ms}}^{+}$ state of ${}^{148}\mathrm{Sm}$.

The neutrino-nucleus cross section and the muon-capture rate are discussed within a simple formalism that facilitates nuclear structure calculations. The corresponding formulas depend on only four types of nuclear matrix elements currently used in nuclear β decay. We have also considered nonlocality effects arising from the velocity-dependent terms in the hadronic current. We show that for both observables in ${}^{12}\mathrm{C}$ the higher order relativistic corrections are of the order of ∼5% only and therefore do not play a significant role. As a nuclear model framework we use the projected quasiparticle random-phase approximation and show that the number projection plays a crucial role in removing the degeneracy between the proton-neutron two-quasiparticle states at the level of the mean field. Comparison is done with both the experimental data and the previous shell model calculations. The possible consequences of the present study on the determination of the ${\nu }_{\mu }\to {\nu }_e$ neutrino oscillation probability are briefly addressed.

We studied the effect of the semiclassical molecular initial ground state configuration of the nucleus on the neutron spectra for $p+\mathrm{Al},\mathrm{Fe}$, and $\mathrm{Zr}$ at 1.2 GeV by using an improved ultrarelativistic quantum molecular dynamics (ImUrQMD) model. Compared to the standard UrQMD version, it incorporates: (i) Pauli potential, (ii) a medium modified $\mathrm{NN}\to N\Delta$ angular distribution, and (iii) a statistical multifragmentation decay model as an afterburner. It is shown that the slow evaporated, cascade, and quasielastic (inelastic) peaks of neutrons are all sensitive to different initialization procedures. Therefore, the implementation of a proper semiclassical ground state initialization in the ImUrQMD model is of importance for the description of all the neutron spectra in proton-induced reactions at intermediate energies $(\approx 1\mathrm{GeV})$.

We estimate the fusion-barrier height $B_{\mathrm{fu}}^{\text{(two-body)}}$ for approaching ions in cold-fusion reactions in a model where the projectile deformation and quadrupole zero-point vibrational energy are taken into account. This barrier height is defined as the barrier energy at the target and projectile separation distance where an original oblate deformation of projectile and/or target caused by a repulsive Coulomb force turns into a large prolate deformation caused by the attractive nuclear force as the target and projectile come closer. The instability develops before touching because the attractive short-range nuclear force overcomes the repulsive Coulomb force and the shape-stabilizing effect of shell structure. The shell structure of the doubly magic ${}^{208}\mathrm{Pb}$ target is sufficiently strong that its shape remains very close to spherical in all cases studied here. The fusion potential for approaching ions in the two-body channel is calculated in the macroscopic-microscopic model with the quadrupole vibrational zero-point energy obtained in the WKB approximation. We compare our results with data from 10 experimental cold-fusion reactions and with the Bass barriers. Differences and similarities between the Yukawa-plus-exponential model and the Bass model are discussed. We also calculate five-dimensional potential-energy surfaces for the single compound system and show that well-established fission and fusion valleys are both present. For heavy systems, $B_{\mathrm{fu}}^{\text{(two-body)}}$ becomes lower than the fission barrier just beyond the ground state of the compound system. In the vicinity of this transition, the optimum collision energy for formation of evaporation residues can be expected to depend in a delicate fashion on the interplay among $B_{\mathrm{fu}}^{\text{(two-body)}}$, the fusion valley, the fission barrier of the compound system, and the one- and two-neutron separation energies $S_{1n}$ and $S_{2n}$. We discuss these issues in detail and calculate fission-barrier heights. Except for reactions in which the projectile is doubly magic or near doubly magic, the calculated quantities are consistent with the observed optimal energies for evaporation-residue formation.