To investigate the importance of pre-equilibrium dynamics on relativistic heavy-ion collision observables, we match a highly nonequilibrium early evolution stage, modeled by free-streaming partons generated from the Monte Carlo Kharzeev-Levin-Nardi (MC-KLN) and Monte Carlo Glauber (MC-Glb) models, to a locally approximately thermalized later evolution stage described by viscous hydrodynamics and study the dependence of final hadronic transverse momentum distributions, in particular their underlying radial and anisotropic flows, on the switching time between these stages. Performing a three-parameter fit of the measured values for the average transverse momenta $\langle p_{\perp }\rangle$ for pions, kaons, and protons, as well as the elliptic and triangular flows of charged hadrons $v_{2,3}^{\mathrm{ch}}$, with the switching time ${\tau }_s$, the specific shear viscosity $\eta /s$ during the hydrodynamic stage, and the kinetic decoupling temperature $T_{\mathrm{dec}}$ as free parameters, we find that the preferred “thermalization” times ${\tau }_s$ depend strongly on the model of the initial conditions. MC-KLN initial conditions require an earlier transition to hydrodynamic behavior (at ${\tau }_s\approx 0.13 \mathrm{fm}/c$), followed by hydrodynamic evolution with a larger specific shear viscosity $\eta /s\approx 0.2$, than MC-Glb initial conditions, which prefer switching at a later time (${\tau }_s\approx 0.6 \mathrm{fm}/c$) followed by a less viscous hydrodynamic evolution with $\eta /s\approx 0.16$. These new results including pre-equilibrium evolution are compared to fits without a pre-equilibrium stage where all dynamic evolution before the onset of hydrodynamic behavior is ignored. In each case, the quality of the dynamical descriptions for the optimized parameter sets, as well as the observables which show the strongest constraining power for the thermalization time, are discussed.

Due to nuclear dissipation, fission cross sections drop with respect to standard statistical model predictions. Using the stochastic dynamical model of fission, we calculate the drop of fission cross sections, ${\sigma }_f^{\mathrm{drop}}$, as a function of presaddle dissipation strength ($\beta$) under two contrasting initial conditions for produced ${}^{224}\mathrm{Th}$ compound nuclei: (i) high excitation energy but low angular momentum (available in spallation reactions) and (ii) low excitation energy but high angular momentum (available in heavy-ion fusion). We find that the former type of conditions not only significantly increases the influence of friction on fission cross sections but also substantially enhances the sensitivity of ${\sigma }_f^{\mathrm{drop}}$ to $\beta$. Our findings suggest that on the experimental side, to accurately obtain information of presaddle friction strength with fission excitation function, it is optimal to choose the spallation reaction approach induced by energetic protons as a way to populate excited nuclear systems.

Using dual-fission chambers each loaded with a thick $(200–400-\mathrm{mg}/\mathrm{c}{\mathrm{m}}^2)$ actinide target of ${}^{235,238}\mathrm{U}$ or ${}^{239}\mathrm{Pu}$ and two thin $(\sim 10–100-\mu \mathrm{g}/\mathrm{c}{\mathrm{m}}^2)$ reference foils of the same actinide, the cumulative yields of fission products ranging from ${}^{92}\mathrm{Sr}$ to ${}^{147}\mathrm{Nd}$ have been measured at $E_n=8.9\mathrm{MeV}$. The ${}^2\mathrm{H}\left(d,n\right){}^3\mathrm{He}$ reaction provided the quasimonoenergetic neutron beam. The experimental setup and methods used to determine the fission product yield (FPY) are described, and results for typically eight high-yield fission products are presented. Our FPYs for ${}^{235}\mathrm{U}\left(n,f\right), {}^{238}\mathrm{U}\left(n,f\right)$, and ${}^{239}\mathrm{Pu}\left(n,f\right)$ at 8.9 MeV are compared with the existing data below 8 MeV from Glendenin et al. [Phys. Rev. C 24, 2600 (1981)], Nagy et al. [Phys. Rev. C 17, 163 (1978)], Gindler et al. [Phys. Rev. C 27, 2058 (1983)], and those of Mac Innes et al. [Nucl. Data Sheets 112, 3135 (2011)] and Laurec et al. [Nucl. Data Sheets 111, 2965 (2010)] at 14.5 and 14.7 MeV, respectively. This comparison indicates a negative slope for the energy dependence of most fission product yields obtained from ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$, whereas for ${}^{238}\mathrm{U}$ the slope issue remains unsettled.

Background: Isoscalar monopole transition has been suggested as a key observable to search for exotic cluster states. Recently, excited $0^{+}$ states with strong isoscalar monopole transition strengths were experimentally reported in ${}^{24}\mathrm{Mg}$, but their structures were not revealed because of the lack of theoretical analysis.

Purpose: We study the structure of the excited $0^{+}$ states of ${}^{24}\mathrm{Mg}$ populated by isoscalar monopole transition from the ground state, and identify their cluster configurations.

Method: The $0^{+}$ states of ${}^{24}\mathrm{Mg}$ and their isoscalar monopole transition strengths from the ground state are calculated with antisymmetrized molecular dynamics combined with the generator coordinate method using the Gogny D1S interaction.

Results: The calculated isoscalar monopole strength function shows reasonable agreement with experiment and is consistent with other theoretical calculations. The structures of the excited $0^{+}$ states with pronounced isoscalar monopole transitions are analyzed. It is found that the $0_2^{+}, 0_3^{+}$, and $0_5^{+}$ states have mixed nature of mean-field and cluster, and that the $0_8^{+}$ state is dominated by a ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ cluster configuration. In addition, it is predicted that $5\alpha \text{-pentagon}+\alpha$ states appear around 23 MeV.

Conclusions: The excited $0^{+}$ states which appear as the prominent peaks in the calculated strength function are associated with ${}^{20}\mathrm{Ne}+\alpha , {}^{12}\mathrm{C}+{}^{12}\mathrm{C}$, and $5\alpha \text{-pentagon+}\alpha$ cluster states.

Two new formulas for the $\left(-2\right)$ moment of the photoabsorption cross section, ${\sigma }_{-2}$, have been determined, respectively, from the 1988 photoneutron evaluation of Dietrich and Berman and a mass-dependent symmetry energy coefficient, $a_{\mathrm{sym}}\left(A\right)$. The data for $A\gtrsim 50$ follow, with a RMS deviation of 6%, the power law ${\sigma }_{-2}=2.4A^{5/3}\mu \mathrm{b}/\mathrm{MeV}$, which is in agreement with Migdal's calculation of ${\sigma }_{-2}=2.25A^{5/3}\mu \mathrm{b}/\mathrm{MeV}$ based on the hydrodynamic model and the ${\sigma }_{-2}$ sum rule. The additional inclusion of $a_{\mathrm{sym}}\left(A\right)$ provides a deeper insight into the nuclear polarization of $A\geqq 10$ nuclei.

Time evolution of an electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The latter is intimately related to the chiral magnetic effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes $k<{\sigma }_{\chi }$ that grow exponentially with time. In the kinematical region relevant for the relativistic heavy-ion collisions, I derive analytical expressions for the magnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times.

We generalize the derivation of viscous anisotropic hydrodynamics from kinetic theory to allow for nonzero particle masses. The macroscopic theory is obtained by taking moments of the Boltzmann equation after expanding the distribution function around a spheroidally deformed local momentum distribution whose form has been generalized by the addition of a scalar field that accounts nonperturbatively (i.e., already at leading order) for bulk viscous effects. Hydrodynamic equations for the parameters of the leading-order distribution function and for the residual (next-to-leading order) dissipative flows are obtained from the three lowest moments of the Boltzmann equation. The approach is tested for a system undergoing ($0+1$)-dimensional boost-invariant expansion for which the exact solution of the Boltzmann equation in the relaxation time approximation is known. Nonconformal viscous anisotropic hydrodynamics is shown to approximate this exact solution more accurately than any other known hydrodynamic approximation.

We precisely determine the infrared (IR) length scale of the no-core shell model (NCSM). In the NCSM, the $A$-body Hilbert space is truncated by the total energy, and the IR length can be determined by equating the intrinsic kinetic energy of $A$ nucleons in the NCSM space to that of $A$ nucleons in a $3(A-1)$-dimensional hyper-radial well with a Dirichlet boundary condition for the hyper radius. We demonstrate that this procedure indeed yields a very precise IR length by performing large-scale NCSM calculations for ${}^6\mathrm{Li}$. We apply our result and perform accurate IR extrapolations for bound states of ${}^4\mathrm{He},{}^6\mathrm{He},{}^6\mathrm{Li}$, and ${}^7\mathrm{Li}$. We also attempt to extrapolate NCSM results for ${}^{10}\mathrm{B}$ and ${}^{16}\mathrm{O}$ with bare interactions from chiral effective field theory over tens of MeV.

${}^{163}\mathrm{Ho}$ to ${}^{163}\mathrm{Dy}$ is, probably due to the small $Q$ value of about 2.5 keV, the best case to determine the neutrino mass by electron capture. The energy of the $Q$ value is distributed between the excitation of dysprosium (and the neglected small recoil of holmium) and the relativistic energy of the emitted neutrino including the rest mass. The reduction of the upper end of the deexcitation spectrum of dysprosium below the $Q$ values allows us to determine the neutrino mass. The excitation of dysprosium can be calculated in the sudden approximation of the overlap of the electron wave functions of holmium minus the captured electron and one-, two-, three-, and multiple hole excitations in dysprosium. Robertson [R. G. H. Robertson, Phys. Rev. C 91, 035504 (2015)] and Faessler and Simkovic [A. Faessler and F. Simkovic, Phys. Rev. C 91, 045505 (2015)] have calculated the influence of the two-hole states on the dysprosium spectrum. Here for the first time the influence of the three-hole states on the deexcitation bolometer spectrum of ${}^{163}$Dy is presented. The electron wave functions and the overlaps are calculated self-consistently in a fully relativistic and antisymmetrized Dirac-Hartree-Fock approach in holmium and in dysprosium. The electron orbitals in Dy are determined including the one-hole states in the self-consistent iteration. The influence of the three-hole states on the Dy deexcitation (by x rays and Auger electrons) can hardly be seen. The three-hole states seem not to be relevant for the determination of the electron neutrino mass.

The earlier study of ${}^{124}\mathrm{Ce}^{*}$ formed in the ${}^{32}\mathrm{S}+{}^{92}\mathrm{Mo}$ reaction at an above barrier beam energy of 150 MeV, using the pocket formula of Blocki et al. for the nuclear proximity potential in the dynamical cluster-decay model (DCM), is extended to the use of other nuclear interaction potentials derived from the Skyrme energy density functional (SEDF) based on the semiclassical extended Thomas Fermi (ETF) approach under the frozen density approximation. The Skyrme forces used are the old SII, SIII, SIV, SKa, SkM, and SLy4 and new GSkI and KDE0(v1), given for both normal and isospin-rich nuclei. It is found that the $\alpha$-nucleus structure, over the non-$\alpha$ nucleus structure, is preferred for only two Skyrme forces, the SIII and KDE0(v1). An extended intermediate mass fragments (IMFs) window, along with the new decay region of heavy mass fragments (HMFs) and the near-symmetric and symmetric fission fragments which, on adding the complementary heavy fragments, corresponds to $(A/2)\pm 12$ mass region of the fusion-fission (ff) process, are predicted by considering cross sections of orders observed in the experiment under study. For the predicted (total) fusion cross section, the survival probability $P_{\mathrm{surv}}$ of the compound nucleus (CN) against fission is shown to be very small because of the very large predicted ff component. On the other hand, the CN formation probability $P_{\mathrm{CN}}$ is found to be nearly equal to 1, and hence the decay under study is a pure CN decay for all the nuclear potentials considered, since the estimated noncompound nucleus (nCN) content is almost negligible. We have also applied the extended-Wong model of Gupta and collaborators, and find that the ${\ell }_{\max }$ values and total fusion cross sections are of the same order as for the DCM. Thus, the extended-Wong model, which describes only the total fusion cross section in terms of the barrier characteristics of the entrance channel nuclei, could be useful for initial experimental studies to be fully treated using the DCM for all the observed decay products.

We perform ab initio no-core shell-model calculations for $A=18$ and 19 nuclei in a $4\hslash \mathrm{\Omega }$, or $N_{\max }=4$, model space by using the effective JISP16 and chiral N3LO nucleon-nucleon potentials and transform the many-body effective Hamiltonians into the $0\hslash \mathrm{\Omega }$ model space to construct the $A$-body effective Hamiltonians in the $sd$ shell. We separate the $A$-body effective Hamiltonians with $A=18$ and $A=19$ into inert core, one-, and two-body components. Then we use these core, one-, and two-body components to perform standard shell-model calculations for the $A=18$ and $A=19$ systems with valence nucleons restricted to the $sd$ shell. Finally, we compare the standard shell-model results in the $0\hslash \mathrm{\Omega }$ model space with the exact no-core shell-model results in the $4\hslash \mathrm{\Omega }$ model space for the $A=18$ and $A=19$ systems and find good agreement.

The role of a strong magnetic field on the neutron-drip transition in the crust of a magnetar is studied. The composition of the crust and the neutron-drip threshold are determined numerically for different magnetic field strengths using the experimental atomic mass measurements from the 2012 Atomic Mass Evaluation complemented with theoretical masses calculated from the Brussels-Montreal Hartree-Fock-Bogoliubov nuclear mass model HFB-24. The equilibrium nucleus at the neutron-drip point is found to be independent of the magnetic field strength. As demonstrated analytically, the neutron-drip density and pressure increase almost linearly with the magnetic field strength in the strongly quantizing regime for which electrons lie in the lowest Landau level. For weaker magnetic fields, the neutron-drip density exhibits typical quantum oscillations. In this case, the neutron-drip density can be either increased by about $14\%$ or decreased by $25\%$ depending on the magnetic field strength. These variations are shown to be almost universal, independently of the nuclear mass model employed. These results may have important implications for the physical interpretation of timing irregularities and quasiperiodic oscillations detected in soft gamma-ray repeaters and anomalous x-ray pulsars, as well as for the cooling of strongly magnetized neutron stars.

Hybrid approaches based on relativistic hydrodynamics and transport theory have been successfully applied for many years for the dynamical description of heavy-ion collisions at ultrarelativistic energies. In this work a new viscous hybrid model employing the hadron transport approach UrQMD for the early and late nonequilibrium stages of the reaction, and 3+1 dimensional viscous hydrodynamics for the hot and dense quark-gluon plasma stage, is introduced. This approach includes the equation of motion for finite baryon number and employs an equation of state with finite net-baryon density to allow for calculations in a large range of beam energies. The parameter space of the model is explored and constrained by comparison with the experimental data for bulk observables from Super Proton Synchrotron and the phase I beam energy scan at Relativistic Heavy Ion Collider. The favored parameter values depend on energy but allow extraction of the effective value of the shear viscosity coefficient over entropy density ratio $\eta /s$ in the fluid phase for the whole energy region under investigation. The estimated value of $\eta /s$ increases with decreasing collision energy, which may indicate that $\eta /s$ of the quark-gluon plasma depends on baryochemical potential ${\mu }_B$.

Based on a chiral approach to nuclear matter, the quartic term in the expansion of the equation of state of isospin-asymmetric nuclear matter is calculated. The contributions to the quartic isospin asymmetry energy $A_4\left(k_f\right)$ arising from $1\pi$ exchange and chiral $2\pi$ exchange in nuclear matter are calculated analytically together with three-body terms involving virtual $\mathrm{\Delta }\left(1232\right)$ isobars. From these interaction terms one obtains at saturation density ${\rho }_0=0.16{\mathrm{fm}}^{-3}$ the value $A_4\left(k_{f0}\right)=1.5\mathrm{MeV}$, more than three times as large as the kinetic energy part. Moreover, iterated $1\pi$ exchange exhibits components for which the fourth derivative with the respect to the isospin asymmetry parameter $\delta$ becomes singular at $\delta =0$. The genuine presence of a nonanalytical term ${\delta }^{4}ln\left|\delta \right|$ in the expansion of the energy per particle of isospin-asymmetric nuclear matter is demonstrated by evaluating an $s$-wave contact interaction at second order.

The cross sections for ${}^{238}\mathrm{Pu}\left(n,f\right)$ reaction for equivalent neutron energy of 13.0–22.0 MeV have been determined by the “surrogate ratio” method by measuring ${}^{235}\mathrm{U}\left({}^6\mathrm{Li},df\right)$ and ${}^{232}\mathrm{Th}\left({}^6\mathrm{Li},df\right)$ transfer induced fission reactions proceeding through the excited fissioning nuclei ${}^{239}\mathrm{Pu}$ and ${}^{236}\mathrm{U}$, respectively, and using ${}^{235}\mathrm{U}\left(n,f\right)$ cross-section data as the reference. Similarly, the cross sections for the ${}^{236}\mathrm{Np}\left(n,f\right)$ reaction in the equivalent neutron energy range 9.9–22.0 MeV have been determined by the “hybrid surrogate ratio” method via the measurements of ${}^{235}\mathrm{U}\left({}^6\mathrm{Li},\alpha f\right)$ and ${}^{235}\mathrm{U}\left({}^6\mathrm{Li},df\right)$ transfer induced fission reactions, using ${}^{238}\mathrm{Pu}\left(n,f\right)$ cross-section data as the reference. The empire-3.1 calculations for ${}^{238}\mathrm{Pu}\left(n,f\right)$ and ${}^{236}\mathrm{Np}\left(n,f\right)$ cross sections agree well with the present data, however, they are slightly underestimated by the endf/b-vii.1 evaluations.

I study the production of a $\psi \left(2S\right)$ meson in heavy ion collisions. I evaluate Wigner functions for the $\psi \left(2S\right)$ meson using both Gaussian and Coulomb wave functions, and investigate the wave function dependence in the $\psi \left(2S\right)$ meson production by recombination of charm and anticharm quarks. The enhanced transverse momentum distribution of $\psi \left(2S\right)$ mesons compared to that of $J/\psi$ mesons, originated from wave function distributions of the $\psi \left(2S\right)$ and $J/\psi$ meson in momentum space, provides a plausible explanation for the recent measurement of the nuclear modification factor ratio between the $\psi \left(2S\right)$ and $J/\psi$ meson.

Hydrodynamic simulations are used to calculate the identical pion Hanbury-Brown–Twiss (HBT) radii, as a function of the pair momentum $k_{\mathrm{T}}$. This dependence is sensitive to the magnitude of the collective radial flow in the transverse plane, and thus comparison to ALICE data enables us to derive its magnitude. By using hydro solutions with variable initial parameters we conclude that in this case fireball explosions start with a very small initial size, well below 1 $\mathrm{fm}$.