We observe an adiabatic separation of collective rotations built upon a subset of intrinsic vibrational states within the interacting boson model (IBM) in the parameter domains corresponding to axially deformed ground state. The effect is not limited only to the low-lying states and closely follows the variation of quantum and classical measures of regularity. It leads to the existence of rotational bands even close to the highest accessible energies in specific regions within the IBM symmetry triangle. We propose a more general effect of regular intrinsic dynamics on the adiabatic separation of intrinsic and collective motion.

With the increasing interest in using ($d,p$) transfer reactions to extract structure and astrophysical information, it is important to evaluate the accuracy of common approximations in reaction theory. Starting from the zero-range adiabatic wave model, which takes into account deuteron breakup in the transfer process, we evaluate the importance of the finite range of the $n\text{−}p$ interaction in calculating the adiabatic deuteron wave (as in Johnson and Tandy) as well as in evaluating the transfer amplitude. Our study covers a wide variety of targets, as well as a large range of beam energies. Whereas at low beam energies finite-range effects are small (below $10\%$), we find these effects to become important at intermediate energies (20 MeV/u) calling for an exact treatment of finite range in the analysis of ($d,p$) reactions measured at fragmentation facilities.

We present music, an implementation of the Kurganov-Tadmor algorithm for relativistic 3+1 dimensional fluid dynamics in heavy-ion collision scenarios. This Riemann-solver-free, second-order, high-resolution scheme is characterized by a very small numerical viscosity and its ability to treat shocks and discontinuities very well. We also incorporate a sophisticated algorithm for the determination of the freeze-out surface using a three dimensional triangulation of the hypersurface. Implementing a recent lattice based equation of state, we compute $p_T$-spectra and pseudorapidity distributions for Au+Au collisions at $\sqrt{s}=200\hspace{0.5em}\mathrm{GeV}$ and present results for the anisotropic flow coefficients $v_2$ and $v_4$ as a function of both $p_T$ and pseudorapidity $\eta$. We were able to determine $v_4$ with high numerical precision, finding that it does not strongly depend on the choice of initial condition or equation of state.

I give a characterization of the conditions for two Hamiltonians to be equivalent, discuss the construction of the operators that relate equivalent Hamiltonians, and introduce variational methods that can select Hamiltonians with desirable features from the space of equivalent Hamiltonians.

For a system with three identical nucleons in a single-$j$ shell, the states can be written as the angular-momentum coupling of a nucleon pair and the odd nucleon. The overlaps between these nonorthonormal states form a matrix that coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. 87, 172501 (2001)]. The propositions they state are related to the eigenvalue problems of the matrix and dimensions of the associated subspaces. In this work, the propositions are proven from the symmetric properties of the $6j$ symbols. Algebraic expressions for the dimension of the states, eigenenergies, as well as conditions for conservation of seniority can be derived from the matrix.

A current objective of low-energy nuclear theory is to build nonempirical nuclear energy density functionals (EDFs) from underlying internucleon interactions and many-body perturbation theory (MBPT). The density matrix expansion (DME) of Negele and Vautherin is a convenient method to map highly nonlocal Hartree-Fock expressions into the form of a quasi-local Skyrme functional with density-dependent couplings. In this work, we assess the accuracy of the DME at reproducing the nonlocal exchange (Fock) contribution to the energy. In contrast to the scalar part of the density matrix for which the original formulation of Negele and Vautherin is reasonably accurate, we demonstrate the necessity to reformulate the DME for the vector part of the density matrix, which is needed for an accurate description of spin-unsaturated nuclei. Phase-space-averaging techniques are shown to yield a significant improvement for the vector part of the density matrix compared to the original formulation of Negele and Vautherin. The key to the improved accuracy is to take into account the anisotropy that characterizes the local momentum distribution in the surface region of finite Fermi systems. Optimizing separately the DME for the central, tensor, and spin-orbit contributions to the Fock energy, one reaches a few-percent accuracy over a representative set of semi-magic nuclei. With such an accuracy at hand, one can envision using the corresponding Skyrme-like energy functional as a microscopically constrained starting point around which future phenomenological parametrizations can be built and refined.

Differential cross sections for $K^{-}$ radiative capture in flight on the proton, leading to the $\gamma \Lambda$ and $\gamma {\Sigma }^0$ final states, have been measured at eight $K^{-}$ momenta between 514 and 750 MeV/$c$. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated $K/\pi$ beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the $\gamma {\Sigma }^0$ final state is dominated by hyperon-resonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the $\gamma \Lambda$ final state, in contrast, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.

We extend our recent study of dilepton invariant-mass spectra from the decays of $\rho$ mesons produced by photon reactions off nuclei. We specifically focus on experimental spectra as recently measured by the CLAS Collaboration at the Thomas Jefferson National Accelerator Facility using carbon and iron nuclei. Building on our earlier work, we broaden our description to a larger set of observables to identify sensitivities to the medium effects predicted by microscopic calculations of the $\rho$ spectral function. We compute mass spectra for several target nuclei and study the spectral shape as a function of the three-momentum of the outgoing lepton pair. We also compute the so-called nuclear transparency ratio, which provides an alternative means (and thus consistency check) of estimating the $\rho$ width in the cold nuclear medium.

We show that the Lagrangian of a free spin-$\frac{5}{2}$ field in the spinor-tensor representation with an auxiliary spinor field depends on three arbitrary parameters. The first two parameters are associated with the spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ sector of the theory while the last is related to the auxiliary degrees of freedom. We derive a corresponding propagator of the system which represents a ($2\times 2$) matrix in the $({\psi }_{\mu \nu },\xi )$ space. The diagonal terms stand for the propagation of the spin-$\frac{5}{2}$ and auxiliary fields whereas the nondiagonal ones correspond to the ${\psi }_{\mu \nu }$-$\xi$ mixing. The resulting spin-$\frac{5}{2}$ propagator contains nonpole contributions coming from the spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ sector of the spinor-tensor representation. A general form of the interaction vertex involving the spin-$\frac{5}{2}$ field is discussed by the example of the $\pi N{N}_{\frac{5}{2}}^{*}$ coupling. It is demonstrated that lower spin degrees of freedom can be removed from the theory by use of higher-order derivative coupling.

The precise determination of the neutron capture cross sections of ${}^{186}\mathrm{Os}$ and ${}^{187}\mathrm{Os}$ is important to define the $s$-process abundance of ${}^{187}\mathrm{Os}$ at the formation of the solar system. This quantity can be used to evaluate the radiogenic component of the abundance of ${}^{187}\mathrm{Os}$ due to the decay of the unstable ${}^{187}\mathrm{Re}$ ($t_{1/2}=41.2$ Gyr) and from this to infer the time duration of the nucleosynthesis in our galaxy (Re/Os cosmochronometer). The neutron capture cross sections of ${}^{186}\mathrm{Os}$, ${}^{187}\mathrm{Os}$, and ${}^{188}\mathrm{Os}$ have been measured at the CERN n_TOF facility from 1 eV to 1 MeV, covering the entire energy range of astrophysical interest. The measurement has been performed by time-of-flight technique using isotopically enriched samples and two ${\mathrm{C}}_6$D${}_6$ scintillation detectors for recording the prompt $\gamma$ rays emitted in the capture events. Maxwellian averaged capture cross sections have been determined for thermal energies between $\mathit{kT}=5$ and 100 keV corresponding to all possible $s$-process scenarios. The estimated uncertainties for the values at 30 keV are 4.1, 3.3, and $4.7\%$ for ${}^{186}\mathrm{Os}$, ${}^{187}\mathrm{Os}$, and ${}^{188}\mathrm{Os}$, respectively.

The inelastic neutron-scattering cross section of ${}^{187}\mathrm{Os}$ has been determined in a time-of-flight experiment at the Karlsruhe $3.7$-MV Van de Graaff accelerator. An almost monoenergetic beam of 30-keV neutrons was produced at the threshold of the ${}^7\mathrm{Li}$($p,n$)${}^7\mathrm{Be}$ reaction. Information on the inelastic channel is required for reliable calculations of the so-called stellar enhancement factor, by which the laboratory cross section of ${}^{187}\mathrm{Os}$ must be corrected in order to account for the thermal population of low-lying excited states at the temperatures of $s$-process nucleosynthesis, in particular of the important state at 9.75 keV. This correction represents a crucial step in the interpretation of the ${}^{187}\mathrm{Os}$/${}^{187}\mathrm{Re}$ pair as a cosmochronometer.

Neutron resonance analyses have been performed for the capture cross sections of ${}^{186}\mathrm{Os}$, ${}^{187}\mathrm{Os}$, and ${}^{188}\mathrm{Os}$ measured at the n_TOF facility at cern. Resonance parameters have been extracted up to 5, 3, and 8 keV, respectively, using the sammy code for a full $R$-matrix fit of the capture yields. From these results average resonance parameters were derived by a statistical analysis to provide a comprehensive experimental basis for modeling of the stellar neutron capture rates of these isotopes in terms of the Hauser-Feshbach statistical model. Consistent calculations for the capture and inelastic reaction channels are crucial for the evaluation of stellar enhancement factors to correct the Maxwellian averaged cross sections obtained from experimental data for the effect of thermally populated excited states. These factors have been calculated for the full temperature range of current scenarios of $s$-process nucleosynthesis using the combined information of the experimental data in the region of resolved resonances and in the continuum. The consequences of this analysis for the $s$-process component of the ${}^{187}\mathrm{Os}$ abundance and the related impact on the evaluation of the time duration of galactic nucleosynthesis via the Re/Os cosmochronometer are discussed.

We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and $\beta$-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in $\beta$-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars.

We calculate the equation of state (EOS) of dense matter using a relativistic mean field (RMF) model with a density dependent coupling that is a slightly modified form of the original NL3 interaction. For nonuniform nuclear matter we approximate the unit lattice as a spherical Wigner-Seitz cell, wherein the meson mean fields and nucleon Dirac wave functions are solved fully self-consistently. We also calculate uniform nuclear matter for a wide range of temperatures, densities, and proton fractions, and match them to nonuniform matter as the density decreases. The calculations took over 6000 CPU days in Indiana University’s supercomputer clusters. We tabulate the resulting EOS at over 107,000 grid points in the proton fraction range $Y_P=0$ to 0.56. For the temperature range $T=0.16$ to 15.8 MeV, we cover the density range $n_B={10}^{-4}$ to 1.6 fm${}^{-3}$; and for the higher temperature range $T=15.8$ to 80 MeV, we cover the larger density range $n_B={10}^{-8}$ to $1.6$ fm${}^{-3}$. In the future we plan to study low density, low temperature ($T<15.8$ MeV), nuclear matter using a Virial expansion, and we will match the low-density and high-density results to generate a complete EOS table for use in astrophysical simulations of supernova and neutron star mergers.

To systematically describe evaporation spectra for light and heavy compound nuclei over a large range of excitation energies, it was necessary to consider three ingredients in the statistical model. First, transmission coefficients or barrier penetration factors for charged-particle emission are typically taken from global fits to elastic-scattering data. However, such transmission coefficients do not reproduce the barrier region of evaporation spectra and reproduction of the data requires a distributions of Coulomb barriers. This is possibly associated with large fluctuations in the compound-nucleus shape or density profile. Second, for heavy nuclei, an excitation-energy dependent level-density parameter is required to describe the slope of the exponential tails of these spectra. The level-density parameter was reduced at larger temperatures, consistent with the expected fadeout of long-range correlation, but the strong $A$ dependence of this effect is unexpected. Last, to describe the angular-momentum dependence of the level density in light nuclei at large spins, the macroscopic rotational energy of the nucleus has to be reduced from the values predicted with the finite-range liquid-drop model.

Superdeformed (SD) states in ${}^{40}\mathrm{Ar}$ have been studied using the deformed-basis antisymmetrized molecular dynamics. Low-energy states were calculated by the parity and angular momentum projection and the generator coordinate method (GCM). Basis wave functions were obtained by the energy variation with a constraint on the quadrupole deformation parameter $\beta$, while other quantities such as triaxiality $\gamma$ were optimized by the energy variation. By the GCM calculation, an SD band was obtained just above the ground-state band. The SD band involves a $K^{\pi }=2^{+}$ side band due to the triaxiality. The calculated electric quadrupole transition strengths of the SD band reproduce the experimental values appropriately. Triaxiality is significant for understanding low-lying states.

The structure of the exact wave function of the isovectorial pairing Hamiltonian with nondegenerate single-particle levels is discussed. The way that the single-particle splittings break the quartet condensate solution found for $N=Z$ nuclei in a single degenerate level is established. After a brief review of the exact solution, the structure of the wave function is analyzed and some particular cases are considered where a clear interpretation of the wave function emerges. An expression for the exact wave function in terms of the isospin triplet of pair creators is given. The ground-state wave function is analyzed as a function of pairing strength, for a system of four protons and four neutrons. For small and large values of the pairing strength a dominance of two-pair (quartets) scalar couplings is found, whereas for intermediate values enhancements of the nonscalar couplings are obtained. A correlation of these enhancements with the creation of Cooper-like pairs is observed.

A quantitative model for the evaluation of the heights of static fission barriers is formulated within the framework of the macroscopic-microscopic approach. In order to describe the main properties (at the ground state and at the saddle point) of superheavy nuclei, a high-dimensional deformation space is used. In the present paper we systematically calculate fission barrier heights $B_f$ for even-even heavy and superheavy nuclei in the range of proton numbers $92⩽Z⩽126$ and neutron numbers $134⩽N⩽192$. Comparisons with experimental data and different theoretical calculations are also shown. The dependence on $B_f$ of fully incorporated, nonaxiality, and reflection-asymmetric degrees of freedom is discussed.

Isotopic effects are studied in reactions induced by ${}^{40}\mathrm{Ca}$ projectiles at 25 MeV/nucleon on ${}^{40}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}$, and ${}^{46}\mathrm{Ti}$ targets. The $N/Z$ contents of projectilelike and midvelocity (MV) sources are probed by means of isotopic (${}^7\mathrm{Li}/{}^6\mathrm{Li}$ and ${}^9\mathrm{Be}/{}^7\mathrm{Be}$) and isobaric (${}^7\mathrm{Li}/{}^7\mathrm{Be}$) yield ratios, for semiperipheral events. In particular, information about isospin transport phenomena will be discussed. Isospin diffusion processes involving nuclei, which have noticeable differences in $N/Z$ have been investigated. Signals of isospin drift, which are related to the gradient of density in the participant region, have also been observed for fragments emitted at MV.

The charge-changing cross sections (${\sigma }_{\mathrm{cc}}$) of ${}^{28}\mathrm{Si}$ on a carbon target were measured with high precision at intermediate energies from 100 to 600 MeV/nucleon. The measured ${\sigma }_{\mathrm{cc}}$ decreases rapidly from low energies up to 200 MeV/nucleon, whereas at higher energies it appears almost constant. The energy dependence of ${\sigma }_{\mathrm{cc}}$ is compared with a Glauber-type model calculation where only the proton distribution of ${}^{28}\mathrm{Si}$ is taken into account. A phenomenological correction factor deduced from the present data satisfactorily reproduces the experimental ${\sigma }_{\mathrm{cc}}$ for other stable nuclei, whose charge distributions were determined by electron scattering and muon capture experiments.