An experimental study of $\omega$ photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The $\gamma p\to \omega p$ differential cross sections are measured from threshold to the incident-photon energy $E_{\gamma }=1.40$ GeV $(W=1.87$ GeV for the center-of-mass energy) with 15-MeV binning in $E_{\gamma }$ and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the $\omega N$ scattering length ${\alpha }_{\omega p}$ is provided.

Cluster formation is a fundamental aspect of the equation of state (EOS) of warm and dense nuclear matter such as can be found in supernovae (SNe). Similar matter can be studied in heavy-ion collisions (HICs). We use the experimental data of Qin et al. [Phys. Rev. Lett. 108, 172701 (2012)] to test calculations of cluster formation and the role of in-medium modifications of cluster properties in SN EOSs. For the comparison between theory and experiment we use chemical equilibrium constants as the main observables. This reduces some of the systematic uncertainties and allows deviations from ideal gas behavior to be identified clearly. In the analysis, we carefully account for the differences between matter in SNe and HICs. We find that, at the lowest densities, the experiment and all theoretical models are consistent with the ideal gas behavior. At higher densities ideal behavior is clearly ruled out and interaction effects have to be considered. The contributions of continuum correlations are of relevance in the virial expansion and remain a difficult problem to solve at higher densities. We conclude that at the densities and temperatures discussed mean-field interactions of nucleons, inclusion of all relevant light clusters, and a suppression mechanism of clusters at high densities have to be incorporated in the SN EOS.

Among about 150 levels below $E_x=5.86\text{MeV}$ in ${}^{208}\mathrm{Pb}$ listed by the Nuclear Data Sheets as of 2007, most levels were recently identified as particle-hole states. All natural parity states excited by the ${}^{208}\mathrm{Pb}(\alpha ,{\alpha }^{\prime })$ reaction are identified, two of them are newly identified. The state at $E_x=5667\text{keV}$ is identified as the $0^{+}$ proton pairing vibration state. Based on the analysis of data from the ${}^{206,207,208}\mathrm{Pb}(d,p),{}^{208}\mathrm{Pb}(d,d^{\prime })$, and ${}^{208}\mathrm{Pb}(p,p^{\prime })$ reactions obtained with the Q3D magnetic spectrograph of the Maier-Leibnitz-Laboratorium at Garching (Germany) at scattering angles ${15}^{\circ }\le \mathrm{\Theta }\le {138}^{\circ }$ and bombarding energies $E_d=22,24\text{MeV}$ and $14.8<E_p<18.2\text{MeV}$, the excitation energy is determined as $E_x=5666.7\pm 0.3\text{keV}$; the mean cross section in the nonresonant ${}^{208}\mathrm{Pb}(p,p^{\prime })$ and the ${}^{208}\mathrm{Pb}(d,d^{\prime })$ reactions is about $1 \mu \text{b/sr}$. A new state at $E_x=5042\pm 3\text{keV}$ is suggested to have the spin of $2^{+}$. The $0^{+}$ neutron pairing vibration state at $E_x=4868\text{keV}$ and the $0^{+}$ member of the double-octupole multiplet at $E_x=5241\text{keV}$ are verified by the nonresonant ${}^{208}\mathrm{Pb}(p,p^{\prime })$ and ${}^{208}\mathrm{Pb}(d,d^{\prime })$ reactions with cross sections of around $3\mu \mathrm{b}/\mathrm{sr}$.

We calculate the quarkonium formation time in relativistic heavy-ion collisions from the space-time correlator of heavy quark vector currents in a hydrodynamic background with the initial nonequilibrium stage expanding only in the longitudinal direction. Using in-medium quarkonia properties determined with the heavy quark potential taken to be the free energy from lattice calculations and the fact that quarkonia can only be formed below their dissociation temperatures due to color screening, we find that $\mathrm{{\rm Y}}$(1S), $\mathrm{{\rm Y}}$(2S), $\mathrm{{\rm Y}}$(3S), $J/\psi$, and ${\psi }^{\prime }$ are formed, respectively, at 1.2, 6.6, 8.8, 5.8, and $11.0\text{fm}/c$ after the quark pair are produced in central Au+Au collisions at the top energy of the BNL Relativistic Heavy Ion Collider (RHIC), and these times become shorter in semicentral collisions. We further show, as an example, that including the effect of formation time enhances appreciably the survivability of $\mathrm{{\rm Y}}$(1S) in the produced hot dense matter.

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity ($\left|y\right|<$ 0.35) in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=62.4$ GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range $1<p_T^e<5$ GeV/$c$. The invariant yield per binary collision is slightly enhanced above the $p+p$ reference in $\mathrm{Au}+\mathrm{Au}$ 0%–20%, 20%–40%, and 40%–60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The $v_2$ of electrons from heavy-flavor decays is nonzero when averaged between $1.3<p_T^e<2.5$ GeV/$c$ for 0%–40% centrality collisions at $\sqrt{s_{NN}}=62.4$ GeV. For 20%–40% centrality collisions, the $v_2$ at $\sqrt{s_{NN}}=62.4$ GeV is smaller than that for heavy-flavor decays at $\sqrt{s_{NN}}=200$ GeV. The $v_2$ of the electrons from heavy-flavor decay at the lower beam energy is also smaller than $v_2$ for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at $\sqrt{s_{NN}}=200$ GeV.

We calculate the production cross section for dileptons, photons, and light vector mesons ($\rho ,\omega$, and $\varphi$) produced by the photoproduction processes in relativistic heavy ion collisions. The jet-quenching effects for fragmentation processes with $p_T>2\mathrm{GeV}$ and the jet-medium interaction with $p_T>4\mathrm{GeV}$ for the fast jets passing through the quark-gluon plasma in Pb-Pb collisions are also considered. The numerical results of photoproduction processes can improve the contribution of dileptons, photons, and light vector meson production in $p-p$ and Pb-Pb collisions at Large Hadron Collider energies.

The proton decay of ${}^{53}\mathrm{Co}^m$($3174.1\text{keV},19/2^{-}$) was investigated via the fragmentation of a ${}^{58}\mathrm{Ni}$ primary beam. The proton-decay energy was determined with an improved precision to be $1558\left(8\right)\text{keV}$. With this new result and the mass of ${}^{53}\mathrm{Co}^m$, the ${}^{52}\mathrm{Fe}$ mass excess was derived to be $-48330\left(8\right)\text{keV}$, which is in good agreement with the AME12 value. A new recommended value of $-48331.6\left(49\right)\text{keV}$ is given.

Background: The linear response of the nucleus to an external field contains unique information about the effective interaction, the correlations governing the behavior of the many-body system, and the properties of its excited states. To characterize the response, it is useful to use its energy-weighted moments, or sum rules. By comparing computed sum rules with experimental values, the information content of the response can be utilized in the optimization process of the nuclear Hamiltonian or the nuclear energy density functional (EDF). But the additional information comes at a price: compared to the ground state, computation of excited states is more demanding.

Purpose: To establish an efficient framework to compute energy-weighted sum rules of the response that is adaptable to the optimization of the nuclear EDF and large-scale surveys of collective strength, we have developed a new technique within the complex-energy finite-amplitude method (FAM) based on the quasiparticle random-phase approximation (QRPA).

Methods: To compute sum rules, we carry out contour integration of the response function in the complex-energy plane. We benchmark our results against the conventional matrix formulation of the QRPA theory, the Thouless theorem for the energy-weighted sum rule, and the dielectric theorem for the inverse-energy-weighted sum rule.

Results: We derive the sum-rule expressions from the contour integration of the complex-energy FAM. We demonstrate that calculated sum-rule values agree with those obtained from the matrix formulation of the QRPA. We also discuss the applicability of both the Thouless theorem about the energy-weighted sum rule and the dielectric theorem for the inverse-energy-weighted sum rule to nuclear density functional theory in cases when the EDF is not based on a Hamiltonian.

Conclusions: The proposed sum-rule technique based on the complex-energy FAM is a tool of choice when optimizing effective interactions or energy functionals. The method is very efficient and well-adaptable to parallel computing. The FAM formulation is especially useful when standard theorems based on commutation relations involving the nuclear Hamiltonian and the external field cannot be used.

The study of the ternary fission of nuclei has received new interest recently. It is of general interest for nuclear dynamics, although the process is very rare. In the present work, we discuss the possibilities of true ternary fission (fragment masses $A>30$) in ${}^{252}\mathrm{Cf}$ for different mass splits. These mass splits are strongly favored in a collinear geometry. Based on the three cluster model (TCM), it is shown that the true ternary fission into fragments with almost equal masses is one of the possible fission modes in ${}^{252}\mathrm{Cf}$. For general decays it is shown that the formation of the lightest fragment at the center has the highest probability. Further the formation of tin isotopes and/or other closed shell fragments are favored. For the decay products the presence of closed shell nuclei among the three fragments enhances the decay probabilities.

We have studied nuclear odd-even mass staggering with the Skyrme-Hartree-Fock-Bogoliubov theory by employing isoscalar and isovector contact pairing interactions. By reproducing the empirical odd-even mass differences of the Sn isotopic chain, the strengths of pairing interactions are determined. The optimal strengths adjusted in this work can give better description of odd-even mass differences than that fitted by reproducing the experimental neutron pairing gap of ${}^{120}\mathrm{Sn}$.

Gamma rays from excited states feeding a proton-emitting isomeric-state in ${}^{151}\mathrm{Lu}$ have been observed for the first time. Comparison with state-of-the-art nonadiabatic quasiparticle calculations indicates an oblately deformed, $3/2^{+}$ proton-emitting state with a quadrupole deformation of ${\beta }_2=-0.11$. The calculations suggest an increase in quadrupole deformation, to ${\beta }_2=-0.18$, with increasing spin which is understood in terms of the mixing of Nilsson states at the Fermi surface. It is also shown that the proton decay half-life is consistent with that from a $3/2^{+}$ state with a quadrupole deformation of ${\beta }_2=-0.12$.

The in-medium masses and optical potentials of $B$ and $\overline{B}$ mesons are studied in an isospin asymmetric, strange, hot, and dense hadronic environment using a chiral effective model. The chiral $\text{SU}\left(3\right)$ model originally designed for the light-quark sector, is generalized to include the heavy-quark sector ($c$ and $b$) to derive the interactions of the $B$ and $\overline{B}$ mesons with the light hadrons. Owing to the large mass of bottom quark, we use only the empirical form of these interactions for the desired purpose, while treating the bottom degrees of freedom to be frozen in the medium. Hence, all medium effects are attributable to the in-medium interaction of the light-quark content of these open bottom mesons. Both $B$ and $\overline{B}$ mesons are found to experience net attractive interactions in the medium, leading to lowering of their masses in the medium. The mass degeneracy of particles and antiparticles, ($B^{+}, B^{-}$) as well as ($B^0, {\overline{B}}^0$), is observed to be broken in the medium, owing to equal and opposite contributions from a vectorial Weinberg-Tomozawa interaction term. Addition of hyperons to the medium lowers further the in-medium mass for each of these four mesons, while a nonzero isospin asymmetry is observed to break the approximate mass degeneracy of each pair of isospin doublets. These medium effects are found to be strongly density dependent and bear a considerably weaker temperature dependence. The results obtained in the present investigation are compared to predictions from the quark-meson coupling model, heavy meson effective theory, and the QCD sum rule approach.

We study the effect of multiple scatterings on the propagation of hard partons and the production of jet-bremsstrahlung photons inside a dense medium in the framework of deep-inelastic scattering off a large nucleus. We include the momentum exchanges in both longitudinal and transverse directions between the hard partons and the constituents of the medium. Keeping up to the second order in a momentum gradient expansion, we derive the spectrum for the photon emission from a hard quark jet when traversing dense nuclear matter. Our calculation demonstrates that the photon bremsstrahlung process is influenced not only by the transverse momentum diffusion of the propagating hard parton, but also by the longitudinal drag and diffusion of the parton momentum. A notable outcome is that the longitudinal drag tends to reduce the amount of stimulated emission from the hard parton.

The results of fully microscopic calculations for the $\alpha$-decay half-lives of light $\alpha$ emitters close to the $N=Z$ line are presented. The ground-state properties are calculated in the relativistic mean field (RMF) approach which reproduce the experiment well, as expected. The $\alpha$-daughter nucleus potential is then calculated in the double folding model using the density dependent M3Y nucleon-nucleon interaction and the RMF nuclear density distributions. This potential in turn is used to calculate the $\alpha$-decay half-lives in the WKB approximation. The results closely agree with the corresponding values obtained by using the available phenomenological expressions as well as with the experiment. The $\alpha$-decay half-lives of a few Te, I, Xe, Cs, and Ba isotopes have also been predicted.

The nucleus ${}^{83}\mathrm{As}$, populated in the neutron-induced fission of ${}^{235}\mathrm{U}$ was studied via prompt $\gamma$-ray spectroscopy using the EXILL Ge array at the cold-neutron beam PF1B of ILL Grenoble. The level scheme is reviewed. The 2779.0-keV level is tentatively assigned spin $(9/2^{+})$ as the $\pi g_{9/2}$ excitation, based on systematics and available shell-model calculations.

A simple two-component shell-model calculation has previously been successful in predicting the absolute energies of $0^{+}{\left(sd\right)}^2$ states in several light nuclei. Here, I apply the same model to such states coupled to odd-A p-shell cores.

Measurements of mass-angle distributions (MADs) for Cr + W reactions, providing a wide range in the neutron-to-proton ratio of the compound system, ${(N/Z)}_{\mathrm{CN}}$, have allowed for the dependence of quasifission on the ${(N/Z)}_{\mathrm{CN}}$ to be determined in a model-independent way. Previous experimental and theoretical studies had produced conflicting conclusions. The experimental MADs reveal an increase in contact time and mass evolution of the quasifission fragments with increasing ${(N/Z)}_{\mathrm{CN}}$, which is indicative of an increase in the fusion probability. The experimental results are in agreement with microscopic time-dependent Hartree-Fock calculations of the quasifission process. The experimental and theoretical results favor the use of the most neutron-rich projectiles and targets for the production of heavy and superheavy nuclei.

The nuclear structure of ${}^{124}\mathrm{Xe}$ has been investigated via measurements of the ${\beta }^{+}$/EC decay of ${}^{124}\mathrm{Cs}$ with the $8\pi \gamma$-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the $2^{+}\to 0^{+}$ in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, $B(E2;2_3^{+}\to 0_2^{+})=78\left(13\right)$ W.u. and $B(E2;2_4^{+}\to 0_3^{+})=53\left(12\right)$ W.u. were determined. The $0_3^{+}$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous ${}^{122}\mathrm{Te}$(${}^3\mathrm{He},n$)${}^{124}\mathrm{Xe}$ measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.