High-spin states in ${}^{76}\mathrm{Sr}$ have been studied using Gammasphere plus Microball detector arrays. The known yrast band has been extended beyond the first band crossing, which involves the simultaneous alignment of pairs of ${\mathrm{g}}_{\frac{9}{2}}$ protons and neutrons, to a tentative spin of $24\hslash$. The data are compared with the results of cranked relativistic mean-field (CRMF) and cranked relativistic Hartree-Bogoliubov (CRHB) calculations. The properties of the band, including the ${\mathrm{g}}_{\frac{9}{2}}$ proton/neutron band crossing frequency and moments of inertia, are found to be well reproduced by the CRHB calculations. Furthermore, the unpaired CRMF calculations show quite good agreement with the data beyond the band crossing region, indicating that pairing is weak at these frequencies. The high spin results suggest that there is little evidence for an isoscalar $(t=0)$ $\mathit{np}$ pair field. Moreover, a systematic study of the band crossings in even-even $N=Z$ nuclei for the first time reveals that there is no evidence to support the existence of the Coulomb antipairing effect caused by the Coulomb exchange term.

The evolution of the symmetry energy coefficient of the binding energy of hot fragments with increasing excitation is explored in multifragmentation processes following heavy-ion collisions below the Fermi energy. In this work, high-resolution mass spectrometric data on isotopic distributions of projectile-like fragments are systematically compared to calculations involving the statistical multifragmentation model (SMM). Within the SMM picture, the present study suggests a gradual decrease of the symmetry energy coefficient of the hot primary fragments from 25 MeV at the compound nucleus regime towards 15 MeV in the multifragmentation regime. The isotopic distributions of the hot primary fragments are found to be very wide and extend towards the neutron drip line. These findings are expected to have important implications in the modeling of the composition and the evolution of hot and dense astrophysical environments, such as those of core-collapse supernova.

The direct and statistical neutron decay of the isoscalar giant dipole resonance was studied in ${}^{90}\mathrm{Zr}$, ${}^{116}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ using the $(\alpha ,{\alpha }^{\text{'}}n)$ reaction at a bombarding energy of 200 MeV. The spectra of fast decay neutrons populating valence hole-states of the $Z,N-1$ nuclei were analyzed, and estimates for the branching ratios were determined. The results were compared to recent continuum random-phase approximation calculations.

Within a self-consistent thermal model using an isospin and momentum dependent interaction (MDI) constrained by the isospin diffusion data in heavy-ion collisions, we investigate the temperature dependence of the symmetry energy $E_{\mathrm{sym}}(\rho ,T)$ and symmetry free energy $F_{\mathrm{sym}}(\rho ,T)$ for hot, isospin asymmetric nuclear matter. It is shown that the symmetry energy $E_{\mathrm{sym}}(\rho ,T)$ generally decreases with increasing temperature while the symmetry free energy $F_{\mathrm{sym}}(\rho ,T)$ exhibits opposite temperature dependence. The decrement of the symmetry energy with temperature is essentially due to the decrement of the potential energy part of the symmetry energy with temperature. The difference between the symmetry energy and symmetry free energy is found to be quite small around the saturation density of nuclear matter. While at very low densities, they differ significantly from each other. In comparison with the experimental data of temperature dependent symmetry energy extracted from the isotopic scaling analysis of intermediate mass fragments (IMF's) in heavy-ion collisions, the resulting density and temperature dependent symmetry energy $E_{\mathrm{sym}}(\rho ,T)$ is then used to estimate the average freeze-out density of the IMF's.

We investigate the $K^{-}$ ${}^3\mathrm{He}$ and $K^{+}{K}^{-}$ interactions in the reaction $\mathit{pd}\to$ ${}^3\mathrm{He}$ $K^{+}{K}^{-}$ near threshold and compare our model calculations with data from the MOMO experiment at COSY-Jülich. A large attractive effective $K^{-}p$ amplitude would give a significant $K^{-}$ ${}^3\mathrm{He}$ final-state interaction effect, which is not supported by the experimental data. We also estimate upper limits for the $a_0(980)$ and $f_0(980)$ contributions to the produced $K^{+}{K}^{-}$ pairs.

Results on $K^{+}$ and $K^0$ meson production in ${}_{44}^{96}\mathrm{Ru}$ + ${}_{44}^{96}\mathrm{Ru}$ and ${}_{40}^{96}\mathrm{Zr}$ + ${}_{40}^{96}\mathrm{Zr}$ collisions at a beam kinetic energy of 1.528$A$ GeV, measured with the FOPI detector at GSI-Darmstadt, are investigated as a possible probe of isospin effects in high-density nuclear matter. The measured double ratio ($K^{+}/K^0$)${}_{\mathrm{Ru}}$/($K^{+}/K^0$)${}_{\mathrm{Zr}}$ is compared to the predictions of a thermal model and a relativistic mean field transport model using two different collision scenarios and under different assumptions on the stiffness of the symmetry energy. We find good agreement with the thermal model prediction and the assumption of a soft symmetry energy for infinite nuclear matter, while more realistic transport simulations of the collisions show a similar agreement with the data but also exhibit a reduced sensitivity to the symmetry term.

Mechanisms for the production of ${}^1{S}_0$ diproton pairs, $\{\mathit{pp}\}{}_s$, in the $\mathit{pd}\to \{\mathit{pp}\}{}_{s}n$ reaction are studied at proton beam energies 0.5–2 GeV in kinematics similar to those of backward elastic $\mathit{pd}$ scattering. This reaction provides valuable information on the short-range $\mathit{NN}$ and $\mathit{pd}$ interactions that is complementary to that investigated in the well-known $\mathit{pd}\to \mathit{dp}$ and $\mathit{dp}\to p(0^{°})X$ processes. The $\mathit{pd}\to \{\mathit{pp}\}{}_{s}n$ reaction is related to the subprocesses ${\pi }^{0}d\to \mathit{pn}$ and $\mathit{pN}\to \{\mathit{pp}\}{}_s\pi$ using two different one-pion-exchange (OPE) diagrams. Within both these models a reasonable agreement could be obtained with the data below 1 GeV. The similar energy dependence of the $\mathit{pd}\to \{\mathit{pp}\}{}_{s}n$ and $\mathit{pd}\to \mathit{dp}$ cross sections and the small ratio of about 1.5% in the production of $\{\mathit{pp}\}{}_s$ to deuteron final states follow naturally within the OPE models.

Recently, we developed a mean-field-type framework that treats the correlation induced by the tensor force. We treat the tensor correlation by introducing intrinsic single-particle states with parity and charge mixing. We make a total wave function with definite charge number and good parity by performing the charge number and parity projections. Taking a variation of the total energy calculated with the projected wave function, we obtain a Hartree-Fock-like equation (charge- and parity-projected Hartree-Fock equation). We extend further the charge- and parity-projected Hartree-Fock method to include a three-body force, which is important to reproduce the saturation property of nuclei in a mean-field framework. We apply the charge- and parity-projected Hartree-Fock method to sub-closed-shell oxygen isotopes (${}^{14}\mathrm{O}$, ${}^{16}\mathrm{O}$, ${}^{22}\mathrm{O}$, ${}^{24}\mathrm{O}$, and ${}^{28}\mathrm{O}$) to study the effect of the tensor correlation and its dependence on neutron number. We obtain reasonable binding energies and matter radii for these nuclei. It is found that relatively large energy gains come from the tensor force in these isotopes and further the blocking effect on the tensor correlation arises due to additional neutrons.

We derive the equation of state of symmetric nuclear matter in a relativistic theory with σ and ω exchange. We take a chiral version of this model which insures all the chiral constraints. Going beyond the mean field approach we introduce the effects of the pion loops. For the parameters of the model, in order to fix those linked to pion exchange, we exploit the most recent information on the short-range part of the spin-isospin interaction. For those linked to the scalar meson exchange we make use of an analysis of lattice results on the nucleon mass evolution with the quark mass. With these inputs we are able reach a correct description of the saturation properties. From the equation of state of symmetric nuclear matter we also derive the density dependence of the quark condensate and of the QCD susceptibilities.

The cross section for polarized and unpolarized electron-proton scattering is calculated by taking into account radiative corrections in leading and next-to-leading logarithmic approximation. The expression of the cross section is formally similar to the cross section of the Drell-Yan process, where the structure functions of the electron play the role of Drell-Yan probability distributions. The interference of the Born amplitude with the two-photon exchange amplitude (box-type diagrams) is expressed as a contribution to the $K$ factor. It is calculated under the assumption that proton form factors decrease rapidly with the momentum transfer squared and that the momentum is equally shared between the two photons. The calculation of the box amplitude is done when the intermediate state is the proton or the Δ resonance. The results of numerical estimations show that the present calculation of radiative corrections can bring into agreement the conflicting experimental results on proton electromagnetic form factors and that the two-photon contribution is very small.

The equation of state (EOS) of dense supernova matter composed of protons, neutrons, and relativistic electrons is calculated within finite temperature Brueckner Goldstone approach with effective two-body Sussex interaction and compared with asymmetric nuclear matter. Thermal effect on the EOS is studied at temperature 5, 7, and 10 MeV. The EOS of supernova matter is found to be stiffer than the corresponding asymmetric nuclear matter equation of state as expected. Single particle properties like distribution functions and chemical potentials of proton, neutron, and electron are discussed for various values of electron fractions, densities, and temperatures. Distribution function is found to depend on Fermi kinetic energy of respective particles as well as on thermal energy. Chemical potential depends on number density of particles and temperature. It is also seen that the EOS for symmetric nuclear matter at low temperature has same order of magnitude with the recently extracted experimental values within the density range 0.35–0.56 ${\text{fm}}^{-3}$.

The systematics of $g$ factor of the first excited $2^{+}$ state vs neutron number $N$ is studied by the projected shell model. The study covers the even-even nuclei of all isotopic chains from Gd to Pt. $g$ factors are calculated by using the many-body wave functions that well reproduce the energy levels and $B(E2)$s of the ground-state bands. For Gd to W isotopes the characteristic feature of the $g$ factor data along an isotopic chain is described by the present model. Deficiency of the model in the $g$ factor description for the heavier Os and Pt isotopes is discussed.

An experiment was performed on ${}^{136}\mathrm{Ce}$ to measure $E2/M1$ multipole mixing ratios using the method of $\gamma \gamma$ angular correlations. The low-spin states of interest were populated by β decay from the $2^{+}$ ground state of ${}^{136}\mathrm{Pr}$ that has a half-life of 13.1 min. Emitted γ rays were detected with the Stony Brook cube germanium detector array. Five $E2/M1$ multipole mixing ratios were measured for the first time and two spin and parity quantum numbers were assigned. Candidates for the $2_{1,\mathrm{ms}}^{+}$ state of ${}^{136}\mathrm{Ce}$ were identified from large $M1$ fractions in the $E2/M1$ multipole mixing ratios. The $2_{1,\mathrm{ms}}^{+}$ state is suggested to be fragmented between the closely lying $2_3^{+}$ and $2_4^{+}$ states. A two state mixing scenario is employed for deducing an $F$-spin mixing matrix element of 43(5) keV.

Excited states in ${}^{98,100,102}\mathrm{Mo}$ have been studied via the ${}^{30}\mathrm{Si}+{}^{168}\mathrm{Er}$-induced fission reaction at a beam energy of 142 MeV. Prompt γ rays were detected with the EUROBALL III multidetector array. The level schemes are extended with more than 20 new transitions and interpreted in the framework of a soft-octupole vibration model.

The Extended Theory of Finite Fermi Systems is based on the conventional Landau-Migdal theory and includes the coupling to the low-lying phonons in a consistent way. The phonons give rise to a fragmentation of the single-particle strength and to a compression of the single-particle spectrum. Both effects are crucial for a quantitative understanding of nuclear structure properties. We demonstrate the effects on the electric dipole states in ${}^{208}\mathrm{Pb}$ (which possesses $50\%$ more neutrons then protons) where we calculated the low-lying noncollective spectrum as well as the high-lying collective resonances. Below 8 MeV, where one expects the so-called isovector pygmy resonances, we also find a strong admixture of isoscalar strength that comes from the coupling to the high-lying isoscalar electric dipole resonance, which we obtain at about 22 MeV. The transition density of this resonance is very similar to the breathing mode, which we also calculated. We shall show that the extended theory is the correct approach for self-consistent calculations, where one starts with effective Lagrangians and effective Hamiltonians, respectively, if one wishes to describe simultaneously collective and noncollective properties of the nuclear spectrum. In all cases for which experimental data exist the agreement with the present theory results is good.

Shell model calculations have been performed for the neutron deficient Cd nuclei from $N=50$ through $N=58$. The nucleus ${}^{88}\mathrm{Sr}$ is taken to be an inert core with valence protons filling the $\{2p_{1/2},1g_{9/2}\}$ orbitals and neutrons the $\{2d_{5/2},3s_{1/2},2d_{3/2},1g_{7/2},1h_{11/2}\}$ orbitals. Using a realistic effective interaction, we have calculated the energy spectra and transition probabilities in ${}^{98,100,102,104,106}\mathrm{Cd}$. We have also made predictions about the presence of mixed-symmetry states that are in good agreement with the corresponding experimental data in ${}^{106}\mathrm{Cd}$.

The four-body equations of Alt, Grassberger, and Sandhas are solved for $n\text{−}$${}^3\mathrm{H}$ scattering at energies below three-body breakup threshold using various realistic interactions including one derived from chiral perturbation theory. After partial wave decomposition the equations are three-variable integral equations that are solved numerically without any approximations beyond the usual discretization of continuum variables on a finite momentum mesh. Large number of two-, three-, and four-nucleon partial waves are considered until the convergence of the results is obtained. The total $n\text{−}$${}^3\mathrm{H}$ cross section data in the resonance region is not described by the calculations which confirms previous findings by other groups. Nevertheless the numbers we get are slightly higher and closer to the data than previously found and depend on the choice of the two-nucleon potential. Correlations between the $A_y$ deficiency in $n\text{−}d$ elastic scattering and the total $n\text{−}$${}^3\mathrm{H}$ cross section are studied.

The relativistic one-boson-exchange model for $\mathit{NN}$ scattering is extended by including two-pion exchange (TPE) contributions in the kernel. We develop the formalism for the evaluation of the TPE diagrams within the relativistic quasipotential approach. The peripheral partial waves in elastic $\mathit{NN}$ scattering are studied within this model. The TPE interactions contain a strongly attractive isoscalar-scalar component which requires a low value of the cutoff parameter: $\Lambda =650\text{−}800$ MeV. With this prescription, the peripheral waves can be reasonably described.

A comprehensive set of ${}^4\mathrm{He}$$(\gamma ,n)$ absolute cross-section measurements was performed at MAX-lab in Lund, Sweden. Tagged photons from $23<E_{\gamma }<70$ MeV were directed toward a liquid ${}^4\mathrm{He}$ target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for 14 photon energies. The results have been subjected to complementary transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as recoil-corrected continuum shell-model, resonating group method, and effective interaction hyperspherical-harmonic expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983.

We study, in the dynamically evolving quark-gluon plasma (QGP) fireball formed in relativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC), the growth of strangeness yield toward and beyond the chemical equilibrium. We account for the contribution of the direct strangeness production and evaluate the thermal-QCD strangeness production mechanisms. The specific yield of strangeness per entropy, $s/S$, is the primary target variable. We explore the effect of collision impact parameter, i.e., fireball size, on kinetic strangeness chemical equilibration in QGP. Insights gained in studying the RHIC data with regard to the dynamics of the fireball are applied to the study of strangeness production at the LHC. We use these results and consider the strange hadron relative particle yields at RHIC and LHC in a systematic fashion. We consider both the dependence on $s/S$ and the direct dependence on the participant number.