We investigate the interaction of neutrinos and antineutrinos with nuclei. We explore, in particular, the role played by multinucleon excitations, which can contaminate the quasielastic cross section. For neutrinos the multinucleon term produces a sizable increase in the quasielastic cross section. Part of the effect arises from tensor correlations. For antineutrinos this influence is smaller, owing to the axial-vector interference, which increases the relative importance of the terms that are not affected by these multinucleon excitations.

Elastic and inelastic scattering of 240-MeV ${}^6\mathrm{Li}$ particles from ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$ were measured with the multipole-dipole-multipole spectrometer from $4^{°}⩽{\theta }_{\mathrm{c}.\mathrm{m}.}⩽{40}^{°}$. Optical potential parameters were obtained by fitting the elastic-scattering data with the double-folding model using the density-dependent M3Y $\mathit{NN}$ effective interaction and $B(E2)$ and $B(E3)$ values obtained for low-lying $2^{+}$ and $3^{-}$ states agreed with the adopted values. The results are compared with those obtained using potentials derived from the systematics of potentials previously obtained for ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, ${}^{58}\mathrm{Ni}$, and ${}^{90}\mathrm{Zr}$. Cross sections for excitation of giant resonances were also calculated with the potentials obtained.

We study the rapidity spectra in ultrarelativistic heavy-ion collisions in the framework of the Landau hydrodynamical model. We find that thermal smearing effects improve the agreement with experimental results on pion rapidity spectra. We describe a simple model of the hadronization and discuss its consequences regarding the pion multiplicity and the increasing entropy condition.

We compute the thermal conductivity of color-flavor-locked (CFL) quark matter. At temperatures below the scale set by the gap in the quark spectrum, transport properties are determined by collective modes. In this work we focus on the contribution from the lightest modes, the superfluid phonon and the massive neutral kaon. The calculation is done in the framework of kinetic theory, using variational solutions of the linearized Boltzmann equation. We find that the thermal conductivity owing to phonons is ${\kappa }^{(P)}~1.04\times {10}^{26}\hspace{0.5em}{\mu }_{500}^8{\Delta }_{50}^{-6}\hspace{0.5em}\mathrm{erg}\mathrm{\hspace{0.5em}}{\mathrm{cm}}^{-1}\mathrm{\hspace{0.5em}}{\mathrm{s}}^{-1}\mathrm{\hspace{0.5em}}{\mathrm{K}}^{-1}$ and the contribution of kaons is ${\kappa }^{(K)}~2.81\times {10}^{21}\hspace{0.5em}{f}_{\pi ,100}^4{T}_{\mathrm{MeV}}^{1/2}{m}_{10}^{-5/2}\hspace{0.5em}\mathrm{erg}\mathrm{\hspace{0.5em}}{\mathrm{cm}}^{-1}\mathrm{\hspace{0.5em}}{\mathrm{s}}^{-1}\mathrm{\hspace{0.5em}}{\mathrm{K}}^{-1}$. These values are smaller than previous estimates but still much larger than (in the case of phonons) or similar to (for kaons) the corresponding values in nuclear matter. From the phonon thermal conductivity we estimate that a CFL quark matter core of a compact star becomes isothermal on a time scale of a few seconds.

We derive a purely fermionic no-sea effective theory, featuring positive-energy states only for the Walecka model. In contrast to the so-called mean-field theory approach with the no-sea approximation, where the Dirac sea is simply omitted from the outset, we turn to the relativistic Hartree approximation and explicitly construct a no-sea effective theory from the underlying quantum field theory. Several results obtained within these two approaches are confronted with each other. This sheds new light on the reliability of the mean-field theory with the no-sea approximation as well as the role of the Dirac sea. Restricting to $1+1$ dimensions, we obtain new analytical insights into nonuniform nuclear matter.

The kinematics of the decay of a bound proton is governed by the proton spectral function. We evaluate this quantity in ${}^{16}\mathrm{O}$ using the information from nuclear physics experiments. It also includes a correlated part. The reliability of this evaluation is sufficient to open the possibility of correlated cuts in the missing mass and momentum variables to identify the decay events from the bound protons with a possible increase of the signal-to-noise ratio.

Cross sections for radiative capture of neutrons have been measured for stable isotopes of Ru with mass numbers $96,102$, and $104$. From separate irradiations using thermal and epithermal neutrons, independent values for the thermal cross section and effective resonance integral have been determined. Spectroscopic studies of the $\gamma$ rays emitted in the decays of ${}^{97,103,105}\mathrm{Ru}$ have enabled improvements in the precision of the energies and intensities of the radiations along with corresponding improvements in the $\beta$-decay feeding intensities and the energies of the levels in the respective daughter nuclei. Similar spectroscopic measurements of the decays of ${}^{105}\mathrm{Rh}$ (daughter of ${}^{105}\mathrm{Ru}$) and ${}^{96}\mathrm{Tc}$ (produced from $n,p$ reactions on ${}^{96}\mathrm{Ru}$) have resulted in improved $\gamma$-ray energies and intensities in those decays.

The framework of relativistic energy-density functionals is extended to include correlations related to the restoration of broken symmetries and to fluctuations of collective variables. The generator coordinate method is used to perform configuration mixing of angular-momentum-projected wave functions, generated by constrained self-consistent relativistic mean-field calculations for triaxial shapes. The effects of triaxial deformation and of $K$ mixing is illustrated in a study of spectroscopic properties of low-spin states in ${}^{24}\mathrm{Mg}$.

Two-body matrix elements of arbitrary local interactions are written as the sum of separable terms in a way that is well suited for the exchange and pairing channels present in mean-field calculations. The expansion relies on the transformation to center of mass and relative coordinate (in the spirit of Talmi’s method) and therefore it is only useful (finite number of expansion terms) for harmonic oscillator single particle states. The converge of the expansion with the number of terms retained is studied for a Gaussian two body interaction. The limit of a contact (delta) force is also considered. Ways to handle the general case are also discussed.

The isospin dependence of the effective pairing interaction is discussed on the basis of the Bardeen, Cooper, and Schrieffer theory of superfluid asymmetric nuclear matter. It is shown that the energy gap, calculated within the mean field approximation in the range from symmetric nuclear matter to pure neutron matter, is not linearly dependent on the symmetry parameter owing to the nonlinear structure of the gap equation. Moreover, the construction of a zero-range effective pairing interaction compatible with the neutron and proton gaps in homogeneous matter is investigated, along with some recent proposals of isospin dependence tested on the nuclear data table.

Fusion excitation functions and angular distributions of evaporation residues (ERs) have been measured for ${}^{28}\mathrm{Si}+{}^{90,94}\mathrm{Zr}$ systems around the Coulomb barrier using the recoil mass spectrometer, Heavy Ion Reaction Analyzer (HIRA). For both systems, the experimental fusion cross sections are strongly enhanced compared to the predictions of the one-dimensional barrier penetration model (1-d BPM) below the barrier. Coupled channels formalism has been employed to theoretically explain the observed sub-barrier fusion cross section enhancement. The enhancement could be explained by considering the coupling of the low-lying inelastic states of the projectile and target in the ${}^{28}\mathrm{Si}+{}^{90}\mathrm{Zr}$ system. In the sub-barrier region, the measured fusion cross sections for ${}^{28}\mathrm{Si}+{}^{94}\mathrm{Zr}$ turned out to be about an order of magnitude higher than the ones for the ${}^{28}\mathrm{Si}+{}^{90}\mathrm{Zr}$ system, which could not be explained by coupling to inelastic states alone. This observation indicates the importance of multinucleon transfer reaction channels with positive $Q$ values in the sub-barrier fusion cross section enhancement, because ${}^{90,94}\mathrm{Zr}$ are believed to have similar collective strengths. This implies that no strong isotopic dependence of fusion cross sections is expected as far as the couplings to collective inelastic states are concerned. In addition, the role of projectile and multiphonon couplings in the enhancement has been explored.

High-energy heavy-ion collisions are studied to access nuclear-matter properties at high density. Particular attention is paid to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent transport simulations built on effective theories, we test isospin observables ranging from nucleon and cluster emissions to collective flows (in particular the elliptic, squeeze-out, part). The effects of the competition between stiffness and momentum dependence of the symmetry potential on the reaction dynamics are thoroughly analyzed. In this way we try to shed light on the controversial neutron and proton effective mass splitting at high baryon and isospin densities. New, more exclusive, experiments are suggested.

We examine the stability of hadron resonance gas models by extending them to include undiscovered resonances through the Hagedorn formula. We find that the influence of unknown resonances on thermodynamics is large but bounded. We model the decays of resonances and investigate the ratios of particle yields in heavy-ion collisions. We find that observables such as hydrodynamics and hadron yield ratios change little upon extending the model. As a result, heavy-ion collisions at the RHIC and LHC are insensitive to a possible exponential rise in the hadronic density of states, thus increasing the stability of the predictions of hadron resonance gas models in this context. Hadron resonance gases are internally consistent up to a temperature higher than the crossover temperature in QCD, but by examining quark number susceptibilities we find that their region of applicability ends below the QCD crossover.

Within an extended chiral constituent quark model, the three- and five-quark structure of the $S_{01}$ resonance $\Lambda (1405)$ is investigated. Helicity amplitudes for electromagnetic decays [$\Lambda (1405)\to \Lambda (1116)\gamma$, $\Sigma (1194)\gamma$] and transition amplitudes for strong decays [$\Lambda (1405)\to \Sigma (1194)\pi$, $K^{-}p$] are derived, as well as the relevant decay widths. The experimental value for the strong decay width, ${\Gamma }_{\Lambda (1405)\to (\Sigma \pi ){}^{°}}=50\pm 2$ MeV, is well reproduced with about $50\%$ of a five-quark admixture in the $\Lambda (1405)$. Important effects owing to the configuration mixing among ${\Lambda }_1^2{P}_A$, ${\Lambda }_8^2{P}_M$, and ${\Lambda }_8^4{P}_M$ are found. In addition, transitions between the three- and the five-quark components in the baryons turn out to be significant in both radiative and strong decays of the $\Lambda (1405)$ resonance.

Motivated by a canonical QCD Hamiltonian, we propose an effective Hamiltonian to represent an arbitrary number of quarks in hadronic bags. The structure of the effective Hamiltonian is discussed and the BCS-type solutions that may represent constituent quarks are presented. The single-particle orbitals are chosen as three-dimensional harmonic oscillators, and we discuss a class of exact solutions that can be obtained when a subset of single-particle basis states is restricted to include a certain number of orbital excitations. The general problem, which includes all possible orbital states, can also be solved by combining analytical and numerical methods.

We investigate weak nuclear decays with extremely small kinetic energy release ($Q$ value) and thus extremely good sensitivity to the absolute neutrino mass scale. In particular, we consider decays into excited daughter states, and we show that partial ionization of the parent atom can help to tune $Q$ values to $\ll 1$ keV. We discuss several candidate isotopes undergoing ${\beta }^{\pm }$, bound state $\beta$, or electron capture decay and come to the conclusion that a neutrino mass measurement using low-$Q$ decays might only be feasible if no ionization is required and if future improvements in isotope production technology, nuclear mass spectroscopy, and atomic structure calculations are possible. Experiments using ions, however, are extremely challenging because of the large number of ions that must be stored. New precision data on nuclear excitation levels could help to identify further isotopes with low-$Q$ decay modes and possibly less challenging requirements.

We analyze the one-boson-exchange potential from the point of view of renormalization theory. We show that the nucleon-meson Lagrangian, while predicting the $\mathit{NN}$ force, does not predict the $\mathit{NN}$ scattering matrix nor the deuteron properties unambiguously due to the appearance of short distance singularities. While the problem has traditionally been circumvented by introducing vertex functions via phenomenological strong form factors, we propose to impose physical renormalization conditions on the scattering amplitude at low energies. Working in the large $N_c$ approximation with $\pi$, $\sigma$, $\rho$, and $\omega$ mesons we show that, once these conditions are applied, results for low-energy phases of proton-neutron scattering as well as deuteron properties become largely insensitive to the form factors and to the vector mesons yielding reasonable agreement with the data and for realistic values of the coupling constants.

Spectra of the ${}^{235}\mathrm{U}$($\gamma ,{\gamma }^{\prime }$) reaction were measured at the S-DALINAC at bremsstrahlung end-point energies $E_0=3.5$ and $4.4$ MeV and scattering angles of ${90}^{°}$ and ${135}^{°}$ with respect to the beam axis. Discrete transitions are observed at excitation energies below $2.3$ MeV only. The deduced cross sections are in rough agreement with the findings of Bertozzi et al. [Phys. Rev. C 78, 041601(R) (2008)] except for the most prominent transition, where the present result is lower by a factor of about $2$. Evidence for unresolved dipole strength is found in the spectra by means of a fluctuation analysis, which was carried out up to an excitation energy of $2.8$ MeV. If this unresolved strength exhibits the same ratio of $E1/M1$ cross sections as observed in the even-mass neighbor ${}^{236}\mathrm{U}$, then the energy centroid ${\overline{E}}_x=2.5(3)$ MeV and total strength $\sum B(M1)\uparrow =3.6(1.3){\mu }_N^2$ of the $M1$ part are in good agreement with the systematics of the scissors mode in even-even actinide nuclei.

We study the fusion reactions of the ${}^{72}\mathrm{Ge}+{}^{72}\mathrm{Ge}$ and ${}^{74}\mathrm{Ge}+{}^{74}\mathrm{Ge}$ systems in terms of the full order coupled-channels formalism. We obtain the fusion excitation function as well as the fusion barrier distribution of these reactions using the coupling matrix suggested from the recent Coulomb excitation experiments. We compare those results with the results obtained by the coupling matrix based on the pure vibrational and rotational models. The barrier distribution for the ${}^{74}\mathrm{Ge}+{}^{74}\mathrm{Ge}$ reaction obtained with the experimental coupling matrix is in good agreement with that obtained with the vibrational model, in contrast to the rotational model. On the other hand, the calculations for ${}^{72}\mathrm{Ge}+{}^{72}\mathrm{Ge}$ system show that the fusion barrier distribution obtained with the experimental coupling matrix significantly differs from those obtained with vibrational and rotational models. Our study indicates that the shape of ${}^{74}\mathrm{Ge}$ is closer to spherical than to deformed, while ${}^{72}\mathrm{Ge}$ has a shape admixture in its ground state, which can be described by neither the vibrational nor the rotational models, as suggested by the Coulomb excitation experiments. This finding will resolve the debates concerning the structure of these nuclei.

The effects of initial state fluctuations on elliptic flow are investigated within a $(3+1)$-dimensional $\mathrm{Boltzmann}+\mathrm{hydrodynamics}$ transport approach. The spatial eccentricity (${\epsilon }_{\mathrm{RP}}$ and ${\epsilon }_{\mathrm{part}}$) is calculated for initial conditions generated by a hadronic transport approach (ultrarelativistic quantum molecular dynamics). Elliptic flow results as a function of impact parameter, beam energy, and transverse momentum for two different equations of state and for averaged initial conditions or a full event-by-event setup are presented. These investigations allow the conclusion that in mid-central ($b=5$–$9$ fm) heavy-ion collisions the final elliptic flow is independent of the initial state fluctuations and the equation of state. Furthermore, it is demonstrated that most of the $v_2$ is built up during the hydrodynamic stage of the evolution. Therefore, the use of averaged initial profiles does not contribute to the uncertainties of the extraction of transport properties of hot and dense QCD matter based on viscous hydrodynamic calculations.