Muonic transition energies in lowlying ${\mu }^{-}-{}^{90}\mathrm{Zr}$ and ${\mu }^{-}-{}^{208}\mathrm{Pb}$ states are reanalyzed by using nuclear polarization with the full-electromagnetic nuclear response. The possibility of the observed enhancement of the energy-weighted sum rule is also considered in the analysis. The transverse part of the nuclear polarization and the enhancement effect play an important role in improving the fine structure splitting of muonic $p$-states in both nuclei. Furthermore, introducing a pygmy dipole resonance in the excitation spectrum, the final fit drastically improves in ${}^{208}\mathrm{Pb}$. However, there remains a discrepancy in ${}^{90}\mathrm{Zr}$, for which the structure of the nuclear excitation spectrum is insensitive to the nuclear-polarization energy shift. Therefore, the remaining discrepancy might be caused by effects other than the nuclear polarization.

Higgs algebras are used to construct rotational Hamiltonians. The correspondence between the spectrum of a triaxial rotor and the spectrum of a cubic Higgs algebra is demonstrated. It is shown that a suitable choice of the parameters of the polynomial algebra allows for a precise identification of rotational properties. The harmonic limit is obtained by a contraction of the algebra, leading to a linear symmetry.

Here we present a self-consistent quasiparticle model for quark-gluon plasma (QGP) and apply it to explain the nonideal behavior seen in lattice simulations. The basic idea, borrowed from electrodynamic plasma, is that the gluons acquire mass as they propagate through plasma due to collective effects and are approximately equal to the plasma frequency. The statistical mechanics and thermodynamics of such a system is studied by treating it as an ideal gas of massive gluons. Since mass or plasma frequency depend on density, which itself is a thermodynamic quantity, the whole problem needs to be solved self-consistently. This new quasiparticle model of QGP explains remarkably well the lattice simulation results of gluon plasma by adjusting just a single phenomenological parameter. Further, we extend our model to study gluon plasma using the exact, ultrarelativistic dispersion relation and again obtain a good fit to lattice results.

Proton threshold states in ${}^{23}\mathrm{Mg}$ are important for the astrophysically relevant proton capture reaction ${}^{22}\mathrm{Na}$($p,\gamma$)${}^{23}\mathrm{Mg}$. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity-assignments remained experimentally uncertain. We have investigated these states with shell model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties, we relate the lowest relevant resonance state at $E_x=7643$ keV to an excited $3/2^{+}$ state in accordance with a recent experimental determination by Jenkins et al. From this we deduce significantly improved values for the ${}^{22}\mathrm{Na}$($p,\gamma$)${}^{23}\mathrm{Mg}$ reaction rate at stellar temperatures below $T_9=0.1$ K.

Theoretical estimates of α-decay half-lives of several nuclei in the decay from element 113 are presented. Calculations in a WKB framework using DDM3Y interaction and experimental Q-values are in good agreement with the experimental data. Half-life calculations are found to be quite sensitive to the Q-values and angular momentum transfers. Calculated decay lifetime decreases, owing to more penetrability as well as thinner barrier, as Q-value increases. Deviations to this predominant behavior observed in some recent experimental data may be attributed to nonzero spin-parities in some cases.

We have investigated experimental quasielastic cross sections measured at backward angles and at deep sub-barrier energies for the ${}^{35}\mathrm{Cl}+{}^{105,106,110}\mathrm{Pd}$ and ${}^{32}\mathrm{S}+{}^{110}\mathrm{Pd}$ systems. Since coupling effects are almost negligible at very low bombarding energies, the quasielastic data allow one to determine the diffuseness parameter of the ion-ion potential. For the analyzed reactions we have obtained a surface diffuseness parameter value around $0.58\pm 0.04$ fm.

Density dependent parametrization models of the nucleon-meson effective couplings, including the isovector scalar δ-field, are applied to asymmetric nuclear matter. The nuclear equation of state and the neutron star properties are studied in an effective Lagrangian density approach, using the relativistic mean field hadron theory. It is known that the introduction of a δ-meson in the constant coupling scheme leads to an increase of the symmetry energy at high density and so to larger neutron star masses, in a pure nucleon-lepton scheme. We use here a more microscopic density dependent model of the nucleon-meson couplings to study the properties of neutron star matter and to reexamine the δ-field effects in asymmetric nuclear matter. Our calculations show that, due to the increase of the effective δ coupling at high density, with density dependent couplings the neutron star masses in fact can be even reduced.

We propose a method for solving exactly the nuclear eigenvalue problem within a multiphonon space constructed out of Tamm-Dancoff phonons. The method consists in deriving, within a given $n$-phonon subspace, a set of equations, of simple structure for any $n$, which are solved iteratively, starting from the particle-hole vacuum, to yield a set of states covering a multiphonon space up to an arbitrary number of phonons. The intrinsic redundancy of the set so generated is removed completely and exactly by a simple and efficient prescription. Such a multiphonon basis reduces the Hamiltonian into diagonal blocks plus residual off-diagonal terms of simple form. Its diagonalization becomes straightforward and yields exact eigensolutions. ${}^{16}\mathrm{O}$ is adopted as numerical test ground.

Model dependence of the reaction rates for the weak breakup of deuterons by low-energy neutrinos is studied starting from the cross sections derived from potential models and also from pionless effective field theory. Choosing the spread of the reaction yields, caused basically by the different ways the two-body currents are treated, as a measure of the model-dependent uncertainty, we conclude that the breakup reactions are $\sim 2\text{–}3\%$ uncertain and that even the ratio of the charged to neutral current reaction rates is also $\sim 2\%$ uncertain.

With the experimental data from the STAR, PHENIX, and BRAHMS programs on the centrality and rapidity dependence of the $p_T$ spectrum in Au+Au and $d+\mathrm{Au}$ collisions, we show that a scaling distribution exists that is independent of the colliding system, centrality, and rapidity. The parameter for the average transverse momentum $\langle p_T\rangle$ increases from peripheral to central $d+$Au collisions. This increase accounts for the enhancement of particle production in those collisions. A nonextensive entropy is used to derive the scaling function.

We continue a series of numerical experiments on many-body systems with random two-body interactions, by examining correlations in ratios in excitation energies of yrast $J=0,2,4,6,8$ states. Previous studies, limited only to $J=0,2,4$ states, had shown strong correlations in boson systems but not fermion systems. By including $J⩾6$ states and considering different scatter plots, strong correlations between ratios of yrast excitation energies appear in both boson and fermion systems. Such correlations agree with real nuclear data and include the well-known limits of seniority, vibrations, and rotations.

Effective field theory (EFT) is the unique, model independent and systematic low-energy version of QCD for processes involving momenta below the pion mass. A low-energy photonuclear observable in three-body systems, photon polarization parameter at thermal neutron energies is calculated by using pionless EFT up to next-to-next to leading order (N${}^2\mathrm{LO}$). In order to make a comparative study of this model, we compared our results for photon polarization parameter with the realistic Argonne $v_{18}$ two-nucleon and Urbana IX or Tucson-Melbourne three-nucleon interactions. Three-body currents give small but significant contributions to some of the observables in the neutron-deuteron radiative capture cross section at thermal neutron energies. In this formalism the three-nucleon forces are needed up to N${}^2\mathrm{LO}$ for cut-off independent results. Our result converges order by order in low energy expansion and also cut-off independent at this order.

Level densities and spin cut-off factors have been investigated within the microscopic approach based on the BCS Hamiltonian. In particular, the spin cut-off parameters have been calculated at neutron binding energies over a large range of nuclear mass using the BCS theory. The spin cut-off parameters ${\sigma }^2(E)$ have also been obtained from the Gilbert and Cameron expression and from rigid body calculations. The results were compared with their corresponding macroscopic values. It was found that the values of ${\sigma }^2(E)$ did not increase smoothly with $A$ as expected based on macroscopic theory. Instead, the values of ${\sigma }^2(E)$ show structure reflecting the angular momentum of the shell model orbitals near the Fermi energy.

Tilt angles, deformation parameters, angular momenta, and reduced magnetic dipole and electric quadrupole transition probabilities are calculated within the framework of the tilted-axis cranking model for shears bands in the neutron-deficient Pb isotopes ${}^{193}\mathrm{Pb}$ to ${}^{202}\mathrm{Pb}$. The self-consistently calculated quadrupole-deformation parameters for the various configurations lie around ${\varepsilon }_2=-0.1$, and the triaxiality is small. The tilt angle, i.e., the angle between the angular momentum and the nuclear symmetry axis, remains almost constant within each band, showing only a small increase toward higher angular momenta. The angular momentum increases mainly due to the shears effect, which is a step-by-step alignment of high-$j$ proton and neutron orbitals into the direction of the total angular momentum. Calculated and experimental $M1$ transition rates are in good agreement. They decrease with increasing spin within the bands as expected for the shears effect. The calculated $B(E2)$ values show only a weak spin dependence. However, the experimental $B(E2)$ values have large errors, and more accurate data are needed to decide between the present model and a recently suggested geometrical approach.

Applications of an extended version of the Hartree-Fock theory and the random-phase approximation derived from the time-dependent density-matrix theory (TDDM) are presented. In this TDDM-based theory, the ground state is given as a stationary solution of the TDDM equations and the excited states are calculated using the small-amplitude limit of TDDM. The first application presented is an extended Lipkin model in which an interaction term describing a particle scattering is added to the original Hamiltonian so that the damping of a collective state is taken into account. It is found that the TDDM-based theory well reproduces the ground state and excited states of the extended Lipkin model. The quadrupole excitation of the oxygen isotopes ${}^{16,20,22}\mathrm{O}$ is also studied as realistic applications of the TDDM-based theory. It is found that large fragmentation of the giant quadrupole resonance in ${}^{16}\mathrm{O}$ is reproduced, and it is pointed out that the effects of ground-state correlations are quite important for fragmentation. It is also found that the quadrupole states in neutron-rich oxygen isotopes have small spreading widths.

The reaction ${}^6\mathrm{Li}$($\gamma ,{\pi }^{+})$${}^6\mathrm{He}$ was studied over the angular range ${\theta }_{\pi }=40$–150$°$ with the aim of investigating the halo structure of ${}^6\mathrm{He}$. Photons from a bremsstrahlung beam were tagged in the energy range $E_{\gamma }=170$–220 MeV at a resolution of $\Delta E_{\gamma }=630$ keV, and positively charged pions detected using high resolution stacked HpGe detectors. The measured angular distributions for the resolved ${}^6\mathrm{He}$ ground and 1.80 MeV excited states are compared to previous measurements and theoretical calculations based on the impulse approximation. It is deduced that the ground state rms radius of the ${}^6\mathrm{He}$ nucleus may be larger than previously thought and that the first excited 1.80 MeV state may also be a halo state.

We have analyzed ${}^3\mathrm{He}$ scattering from ${}^{12}\mathrm{C}$ at 34.7 and 72 MeV in a coupled channel method with a double folding potential derived from the precise wave functions for the ground $0^{+}$ state and $0_2^{+}$ (7.65 MeV) Hoyle state, which has been suggested to be an $\alpha$ particle condensate. It is found that strong refraction of ${}^3\mathrm{He}$ in the Hoyle state can be clearly seen in the experimental angular distribution at a low incident energy region as an Airy minimum of the prerainbow oscillations.

A generalized method to calculate the excitation-energy dependent parity ratio in the nuclear level density is presented, using the assumption of Poisson distributed independent quasi particles combined with BCS occupation numbers. It is found that it is crucial to employ a sufficiently large model space to allow excitations both from low-lying shells and to higher shells beyond a single major shell. Parity ratios are only found to equilibrate above at least 5–10 MeV of excitation energy. Furthermore, an overshooting effect close to major shells is found where the parity opposite to the ground state parity may dominate across a range of several MeV before the parity ratio finally equilibrates. The method is suited for large-scale calculations as needed, for example, in astrophysical applications. Parity distributions were computed for all nuclei from the proton dripline to the neutron dripline and from Ne up to Bi. These results were then used to recalculate astrophysical reaction rates in a Hauser-Feshbach statistical model. Although certain transitions can be considerably enhanced or suppressed, the impact on astrophysically relevant reactions remains limited, mainly due to the thermal population of target states in stellar reaction rates.

We investigate the ${}^1{S}_0$ neutron and proton superfluidity in isospin-asymmetric nuclear matter. We have concentrated on the isospin dependence of the pairing gaps and the effect of a microscopic three-body force. It is found that as the isospin asymmetry goes higher, the neutron ${}^1{S}_0$ superfluid phase shrinks gradually to a smaller density domain, whereas the proton one extends rapidly to a much wider density domain. The three-body force turns out to weaken the neutron ${}^1{S}_0$ superfluidity slightly, but it suppresses strongly the proton ${}^1{S}_0$ superfluidity at high densities in nuclear matter with large isospin asymmetry.

Differential cross sections for the reaction $\gamma p\to K^{*0}{\Sigma }^{+}$ are presented in the photon energy range of 1.7 to 3.0 GeV. The $K^{*0}$ was detected by its decay products, $K^{+}{\pi }^{-}$, in the Continuous Electron Beam Accelerator Facility's large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility. These data are the first $K^{*0}$ photoproduction cross sections ever published over a broad range of angles. Comparison with a theoretical model based on the vector and tensor $K^{*}$-quark couplings shows good agreement with the data, except at forward angles, suggesting that the role of scalar κ meson exchange should be investigated.