We study the effect of rotation on the global properties of a neutron star with a hyperon core in an effective chiral model with varying nucleon effective masses within a mean-field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range of $(1.4\text{−}2.4)M_{\odot }$ at Kepler frequency ${\Omega }_K$, which is consistent with recent observations of high mass stars, thereby reflecting the sensitivity of the underlying nucleon effective mass in the dense matter equation of state. We also discuss the implications of the experimental constraints from the flow data from heavy-ion collisions on the global properties of rotating neutron stars.

I explore the form of the effective interaction in harmonic-oscillator-based effective theory (HOBET) in leading order (LO) through next-to-next-to-next-to-leading order (N${}^3\mathrm{LO}$). Because the included space in a HOBET (as in the shell model) is defined by the oscillator energy, both long-distance (low-momentum) and short-distance (high-momentum) degrees of freedom reside in the high-energy excluded space. A HOBET effective interaction is developed in which a short-range contact-gradient expansion, free of operator mixing and corresponding to a systematic expansion in nodal quantum numbers, is combined with an exact summation of the relative kinetic energy. By this means the very strong coupling of the included ($P$) and excluded ($Q$) spaces by the kinetic energy is removed. One finds a simple and rather surprising result, that the interplay of $\mathit{QT}$ and $\mathit{QV}$ is governed by a single parameter κ, the ratio of an observable, the binding energy $\left|E\right|$, to a parameter in the effective theory, the oscillator energy $\hslash \omega$. Once the functional dependence on κ is identified, the remaining order-by-order subtraction of the short-range physics residing in $Q$ becomes systematic and rapidly converging. Numerical calculations are used to demonstrate how well the resulting expansion reproduces the running of $H^{\mathrm{eff}}$ from high scales to a typical shell-model scale of $8\hslash \omega$. At N${}^3\mathrm{LO}$ various global properties of $H^{\mathrm{eff}}$ are reproduced to a typical accuracy of 0.01%, or about 1 keV, at $8\hslash \omega$. Channel-by-channel variations in convergence rates are similar to those found in effective field theory approaches. The state dependence of the effective interaction has been a troubling problem in nuclear physics and is embodied in the energy dependence of $H^{\mathrm{eff}}(|E|)$ in the Bloch-Horowitz formalism. It is shown that almost all of this state dependence is also extracted in the procedures followed here, isolated in the analytic dependence of $H^{\mathrm{eff}}$ on κ. Thus there exists a simple, Hermitian $H^{\mathrm{eff}}$ that can be use in spectral calculations. The existence of a systematic operator expansion for $H^{\mathrm{eff}}$, depending on a series of short-range constants augmented by κ, will be important to future efforts to determine the HOBET interaction directly from experiment, rather than from an underlying $\mathit{NN}$ potential.

We study the leading isospin-breaking contributions to the two-nucleon two-pion exchange potential due to explicit Δ degrees of freedom in chiral effective field theory. In particular, we find important contributions due to the delta mass splittings to the charge symmetry breaking potential that act opposite to the effects induced by the nucleon mass splitting.

Using the particle-rotor model (PRM), in which two quasiparticles are coupled to a triaxial core, the negative-parity doublet bands in ${}^{106}\mathrm{Rh}$ are studied. The quadrupole deformations β and γ for the $\pi g_{9/2}\otimes \nu h_{11/2}$ configuration are calculated by configuration-fixed constrained triaxial relativistic mean-field (RMF) approaches, and these self-consistent deformation parameters are used as inputs for the PRM. The present calculated results well reproduce the observed energy spectra, energy staggering parameter, and electromagnetic transition ratios of the doublet bands, thus supporting the chiral interpretation of these doublet bands in ${}^{106}\mathrm{Rh}$. The effective angles between the angular momenta in the body-fixed frame are calculated for the first time. We demonstrate that rigid triaxial deformation can give rise to the experimentally observed constant energy separation between the yrast and side bands built on the asymmetrical $\pi g_{9/2}\otimes \nu h_{11/2}$ configuration in the $A~100$ mass region.

Interaction cross sections (${\sigma }_{\mathrm{I}}$) of ${}^{72,76,80}\mathrm{Kr}$ on a C target were measured at the projectile fragment separator FRS at GSI. Effective matter radii of the nuclei were deduced by a Glauber model analysis so as to reproduce the experimental ${\sigma }_{\mathrm{I}}$. An increase of matter radii toward the proton drip-line is observed. We compare the extracted radii to theoretical predictions, which are based on Skyrme-Hartree-Fock-Bogoliubov (SHFB) and on relativistic mean field (RMF) approaches. The enhancement of the matter radius observed in ${}^{72}\mathrm{Kr}$ is discussed.

We construct microscopic three-nucleon forces consistent with the Bonn and Nijmegen two-nucleon potentials, and including Δ, Roper, and nucleon-antinucleon excitations. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined.

Covariant density functional theory, in the framework of self-consistent relativistic mean field (RMF) and relativistic random-phase approximation (RRPA), is for the first time applied to axially deformed nuclei. The fully self-consistent RMF+RRPA equations are posed for the case of axial symmetry and nonlinear energy functionals and solved with the help of a new parallel code. Formal properties of RPA theory are studied and special care is taken to validate the proper decoupling of spurious modes and their influence on the physical response. Sample applications to the magnetic and electric dipole transitions in ${}^{20}\mathrm{Ne}$ are presented and analyzed.

It is demonstrated by shell-model calculations of $\mathit{sd}$-shell nuclei that the binding energies are dominated by the monopole part of nucleon-nucleon interaction. The monopole component, which comes mainly from the two-body interaction in triplet-even channel, can be renormalized into one-body single-particle energies. It is also shown that the proton-neutron quadrupole interaction causes a sizable gain of binding energy by coherent configuration mixing of quadrupole deformation.

The level densities of ${}^{44}\mathrm{Sc}$ and ${}^{47}\mathrm{Ti}$ have been determined from measurements of particle evaporation spectra from the compound nuclear reaction ${}^3\mathrm{He}+{}^{45}\mathrm{Sc}$ with an 11 MeV ${}^3\mathrm{He}$ beam. The level density of ${}^{44}\mathrm{Sc}$ has been compared to the level density obtained from an independent experimental method based on an analysis of $\alpha \text{−}\gamma$ coincidences from the transfer reaction ${}^{45}\mathrm{Sc}$(${}^3\mathrm{He}$,$\alpha \gamma$)${}^{44}\mathrm{Sc}$. The good agreement between the two experiments indicates the reliability of the level density obtained. Some level density systematics have been tested against the experimental data. New Fermi-gas level density parameters have been derived.

Multiplicity fluctuations in limited segments of momentum space are calculated for a classical pion gas within the statistical model. Results for the grand canonical, canonical, and micro-canonical ensemble are obtained, compared, and discussed. We demonstrate that even in the large volume limit correlations between macroscopic subsystems due to energy and momentum conservation persist. Based on the microcanonical formulation we make qualitative predictions for the rapidity and transverse-momentum dependence of multiplicity fluctuations. The resulting effects are of similar magnitude as the predicted enhancement due to a phase transition from a quark-gluon plasma to a hadron gas phase or due to the critical point of strongly interacting matter and qualitatively agree with recently published preliminary multiplicity fluctuation data of the NA49 SPS experiment.

Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR Collaboration presents a measurement of ${\rho }^0$ and direct ${\pi }^{+}{\pi }^{-}$ photoproduction in ultraperipheral relativistic heavy ion collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross section of $\sigma (\mathrm{AuAu}\to {\mathrm{Au}}^{*}{\mathrm{Au}}^{*}{\rho }^0)=530\pm 19(\mathrm{stat}.)\pm 57(\mathrm{syst}.)$ mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The ${\rho }^0$ transverse momentum spectrum ($p_T^2$) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find ${\sigma }_{\mathrm{inc}}/{\sigma }_{\mathrm{coh}}=0.29\pm 0.03(\mathrm{stat}.)\pm 0.08(\mathrm{syst}.)$. The ratio of direct ${\pi }^{+}{\pi }^{-}$ to ${\rho }^0$ production is comparable to that observed in $\gamma p$ collisions at HERA and appears to be independent of photon energy. Finally, the measured ${\rho }^0$ spin helicity matrix elements agree within errors with the expected $s$-channel helicity conservation.

The longitudinal hydrodynamic expansion of the fluid created in relativistic heavy-ion collisions is considered taking into account shear viscosity. We consider the dynamics of a non-boost-invariant energy density of the fluid in 1+1 dimensions, using the proper time and the space-time rapidity. Both a nonvanishing viscosity and a soft equation of state make the final particle distributions in rapidity narrower. The width of the initial Gaussian rapidity distribution and its central energy density are fitted to reproduce the rapidity distributions of pions and kaons as measured by the BRAHMS Collaboration. The presence of viscosity has dramatic consequences on the value of the initial energy density. Dissipative processes and the reduction of the longitudinal work due to the shear viscosity increase the total entropy and the particle multiplicity at central rapidities. Viscous corrections make the longitudinal velocity of the fluid stay close to the Bjorken scaling flow $v_z=z/t$ through the evolution.

The response of the core nucleus to the Λ in a hypernucleus is studied with a local density approximation. This reproduces the energies and radii of the core nuclei as well as the Λ-single particle (s.p.) energies quite well. The polarizing effect of the Λ depends on the core response through an “effective” compression modulus $K_A$ of the nucleus. For a certain class of energy functional, $K_A$ is found to be almost independent of the compression modulus $K$ of the infinite nuclear matter. This indeed is a surprising result, and varies with the Hartree-Fock calculations with effective interactions. Reasons for this discrepancy are carefully examined. We consider values of $K$ in the range $\approx 100\text{−}400$ MeV. Furthermore, the polarizing effects also depend critically on $D(\rho )$, the Λ binding in nuclear matter at density $\rho$. For only a direct $\Lambda N$ force: $D\propto \rho$ and the core nucleus contracts giving rise to relatively larger core polarization. However, for a “saturating” $D(\rho )$ (with a maximum at ${\rho }_m<{\rho }_0$, where ${\rho }_0$ is the nuclear matter equilibrium density), which is required to fit the s.p. data, the $s$-shell hypernuclei binding energies and the low energy $\Lambda p$ scattering data, which results from a $\Lambda N$ force (including exchange) and $\Lambda \mathit{NN}$ forces, there may be an expansion of the nucleus with nucleons flowing from the interior to the surface. This is shown to reduce the core polarization effects substantially (for ${\rho }_m$ in the neighborhood of ${\rho }_0$). The resulting changes in root mean square radius and core energy depend on $A$, but are mostly very small, justifying their general neglect.

We expand the triaxial projected shell model basis to include triaxially deformed multi-quasiparticle states. This allows us to study the yrast and γ-vibrational bands up to high spins for both γ-soft and well-deformed nuclei. As a first application, a systematic study of the high-spin states in Er isotopes is performed. The calculated yrast and γ bands are compared with the known experimental data, and it is shown that the agreement between theory and experiment is quite satisfactory. The calculation leads to predictions for bands based on one- and two-γ phonons where current data are still sparse. It is observed that γ bands for neutron-deficient isotopes of ${}^{156}\mathrm{Er}$ and ${}^{158}\mathrm{Er}$ are close to the yrast band, and further these bands are predicted to be nearly degenerate for high-spin states.

The superscaling analysis using the scaling function obtained within the coherent density fluctuation model is extended to calculate charge-changing neutrino and antineutrino scattering on ${}^{12}\mathrm{C}$ at energies from 1 to 2 GeV not only in the quasielastic but also in the $\Delta$ excitation region. The results are compared with those obtained using the scaling functions from the relativistic Fermi gas model and from the superscaling analysis of inclusive scattering of electrons from nuclei.

Transverse momentum spectra up to $4.5\mathrm{GeV}/c$ around midrapidity of ${\pi }^{\pm },p,\overline{p}$, and $K^{\pm }$ in $\mathrm{Pb}+\mathrm{Pb}$ reactions were measured at $\sqrt{s_{{}_{\mathit{NN}}}}=17.3\mathrm{GeV}$ by the CERN-NA49 experiment. The nuclear modification factors $R_{\mathit{AA}}$ for ${\pi }^{\pm }$ and $R_{\mathrm{CP}}$ for ${\pi }^{\pm },p,\overline{p},K^{\pm }$ were extracted and compared with results obtained at the BNL Relativistic Heavy Ion Collider (RHIC) at $\sqrt{s_{{}_{\mathit{NN}}}}=200\mathrm{GeV}$. The modification factor $R_{\mathit{AA}}$ shows a rapid increase with transverse momentum in the covered region. This indicates that the Cronin effect is the dominating effect in our energy range. The modification factor $R_{\mathrm{CP}}$, in which the contribution of the Cronin effect is reduced, shows a saturation well below unity in the ${\pi }^{\pm }$ channel. The extracted $R_{\mathrm{CP}}$ values follow the $200\mathrm{GeV}$ RHIC results closely in the available transverse momentum range, except for ${\pi }^{\pm }$ above $2.5\mathrm{GeV}/c$ transverse momentum. There the measured suppression is smaller than that observed at RHIC.

We discuss the quantum mechanical decay of the color magnetic field generated initially during high-energy heavy-ion collisions. The decay is caused by Nielsen-Olesen unstable modes and is accomplished possibly in a period <1 fm/$c$. We show that the decay products (i.e., incoherent gluons) may be thermalized in a sufficiently short period (<1 fm/$c$). The precise determination of the period is made by calculating the two-point function of the color magnetic field in a color glass condensate model.

Particle production in $\mathrm{Au}\text{−}\mathrm{Au}$, $\mathrm{Cu}\text{−}\mathrm{Cu}$, $d$-Au, and $p\text{−}p$ collisions at 200 GeV c.m. energy are analyzed in the wounded quark-diquark model. Existing data are well reproduced. Emission functions of wounded and unwounded constituents are determined. Implications for the collective evolution of the system are discussed.

A simple form for phenomenological nuclear potential is introduced as an alternative to the popular Woods-Saxon (WS) form. In contrast to the WS form the new form becomes exactly zero at a finite distance and all derivatives of this form are continuous everywhere. The sequence of the single-particle levels of a WS potential with realistic parameters can be reproduced reasonably well with the new potential in which even the positions of the broad resonances are free from uncertainties.

We solve the Faddeev equation in an exactly Poincaré invariant formulation of the three-nucleon problem. The dynamical input is a relativistic nucleon-nucleon ($\mathit{NN}$) interaction that is exactly on-shell equivalent to the high-precision CD Bonn $\mathit{NN}$ interaction. $S$-matrix cluster properties dictate how the two-body dynamics is embedded in the three-nucleon mass operator (rest Hamiltonian). We find that for neutron laboratory energies above $\approx 20$ MeV relativistic effects on $A_y$ are negligible. For energies below $\approx 20$ MeV dynamical effects lower the nucleon analyzing power maximum slightly by $\approx 2\%$ and Wigner rotations lower it further up to $\approx 10\%$, thereby increasing disagreement between data and theory. This indicates that three-nucleon forces (3NF) must provide an even larger increase of the $A_y$ maximum than expected up to now.