We investigate the three-body Coulomb breakup of a two-neutron halo nucleus, ${}^6\mathrm{He}$. Based on the $\alpha +n+n$ model, the three-body scattering states of ${}^6\mathrm{He}$ are described by using the combined methods of the complex scaling and the Lippmann-Schwinger equation. We calculate the breakup cross section, the two-dimensional energy distributions, and the invariant mass spectra for the $E1$ transition of ${}^6\mathrm{He}$. We discuss the relations between the structures in these strengths and the $n$-$n$ and $\alpha$-$n$ correlations of ${}^6\mathrm{He}$. It is found that the ${}^5\mathrm{He}$ resonance in the final states contributes to make a low-energy enhancement of the strength. The $n$-$n$ final-state interaction also contributes to enhance the strength globally. However, the ground-state correlations of ${}^6\mathrm{He}$, such as a dineutron, are difficult to recognize in the strength because of the dominant effect of the final-state interaction.

The elastic scattering of ${}^6\mathrm{He}$ on ${}^{120}\mathrm{Sn}$ has been measured at four energies above the Coulomb barrier using the ${}^6\mathrm{He}$ beam produced at the RIBRAS (Radioactive Ion Beams in Brasil) facility. The elastic angular distributions have been analyzed with the optical model and three- and four-body continuum-discretized coupled-channels calculations. The total reaction cross sections have been derived and compared with other systems of similar masses.

We have reevaluated the ${}^{136}\mathrm{Xe}({}^{136}\mathrm{Xe},\mathit{xn}){}^{272-x}\mathrm{Hs}$ reaction with a modified fusion-by-diffusion model. In this model, the early dynamics of neck growth is taken into account in terms of the two-dimensional Langevin equation. By numerically solving the dynamic equations, the probability distribution of the separation between the surfaces of two approaching nuclei at the injection point in an asymmetric fission valley is obtained. Before reaching the asymmetric fission valley, the strong electrostatic repulsion may force the system to redisintegrate in a quasifissionlike process. We find that more than $80\%$ of quasifission events occur during the transition from dinuclear to mononuclear regimes for the ${}^{136}\mathrm{Xe}+{}^{136}\mathrm{Xe}$ reaction. This observation gives credence to the conjecture that the quasifission reaction channel most likely occurs in an early stage of collective motion. By incorporating this essential physical ingredient into the calculations, the modified fusion-by-diffusion model nicely accounts for the experiment of the ${}^{136}\mathrm{Xe}+{}^{136}\mathrm{Xe}$ reaction performed in Dubna.

This work reports ${}^{237}\mathrm{Np}$ neutron resonance parameters obtained from the simultaneous analysis of time-of-flight data measured at the GELINA, ORELA, KURRI, and LANSCE facilities. A statistical analysis of these resonances relying on average $R$-matrix and optical model calculations was used to establish consistent $l$-dependent average resonance parameters involved in the description of the unresolved resonance range of the ${}^{237}\mathrm{Np}$ neutron cross sections. For neutron orbital angular momentum  $l=0$, we obtained an average radiation width $\langle {\Gamma }_{\gamma }\rangle =39.3\pm 1.0$ meV, a neutron strength function ${10}^4{S}_0=1.02\pm 0.14$, a mean level spacing $D_0=0.60\pm 0.03$ eV, and a potential scattering length $R^{\prime }=9.8\pm 0.1$ fm.

True ternary fission with formation of a heavy third fragment is quite possible for superheavy nuclei because of the strong shell effects leading to a three-body clusterization with the two doubly magic tinlike cores. The simplest way to discover this phenomenon in the decay of excited superheavy nuclei is a detection of two tinlike clusters with appropriate kinematics in low-energy collisions of medium-mass nuclei with actinide targets. The three-body quasi-fission process could be even more pronounced for giant nuclear systems formed in collisions of heavy actinide nuclei. In this case a three-body clusterization might be proved experimentally by the detection of two coincident leadlike fragments in low-energy U $+$ U collisions.

A description of exclusive charged-pion electroproduction $(e,e^{\prime }{\pi }^{\pm })$ off nucleons at high energies is proposed. The model combines a Regge pole approach with the residual effect of nucleon resonances. The exchanges of $\pi (140)$, vector $\rho (770)$, and axial-vector $a_1(1260)$ and $b_1(1235)$ Regge trajectories are considered. The contribution of nucleon resonances is described using a dual connection between the exclusive hadronic form factors and inclusive deep inelastic structure functions. The model describes the measured longitudinal, transverse, and interference cross sections at the Thomas Jefferson Lab National Accelerator Facility (JLAB) and the Deutsches Elektronen Synchrotron. The scaling behavior of the cross sections is in agreement with JLAB and deeply virtual HERMES data. The results for a polarized beam-spin azimuthal asymmetry in $(\mathrm{e⃗},e^{\prime }{\pi }^{\pm })$ are presented. Model predictions for JLAB at $12$ GeV are given.

We consider nuclear matter in the frames of the sigma model and find the role of correlation energy in the determination of the parameters of neutron stars. The response-function formalism is used for calculations within the Hartree-Fock approach and beyond. When electrons and muons are present in the neutron-rich matter, the maximal mass of the star is $M_{*}=1.64$ (in the unit of the solar mass $M_{\odot }$). The correlation energy becomes very important for the stars with $M_{*}~0.7÷1.5M_{\odot }$ and its effect is estimated as $0.3÷0.4M_{\odot }$ extracted from the relevant values obtained in the frames of the Hartree-Fock approximation. On the whole, the nuclear equation of state is definitely “softened.”

Effects of difference in the spin and parity distributions for the surrogate and neutron-induced reactions are investigated. Without assuming specific (schematic) spin-parity distributions, it was found that the surrogate ratio method can be employed to determine neutron fission and capture cross sections if (1) weak Weisskopf-Ewing condition (defined in this paper) is satisfied, (2) there exist two surrogate reactions whose spin-parity distributions of the decaying nuclei are almost equivalent, and (3) difference of the representative spin values between the neutron-induced and surrogate reactions is no much larger than $10\hslash$. If these conditions are satisfied, we need not know the spin-parity distributions populated by the surrogate method. Instead, we should just select a pair of surrogate reactions which will populate the similar spin-parity distributions, using targets having similar structure and reactions having the similar reaction mechanisms. Achievable accuracy is estimated to be around $5\%$ and $10\%$ for fission and capture channels, respectively, for nuclei of the Uranium region. The surrogate absolute method may be applicable to determination of fission cross sections with a caution. However, there will be little hope to apply this method for capture cross section measurements unless the spin-parity distributions in the neutron-induced and surrogate reactions are fairly close to each other (which is implausible) or the difference can be corrected theoretically. The surrogate ratio method was shown also to be a robust method in the presence of breakup reactions without assuming specific breakup reaction mechanisms.

The deuteron breakup reaction $\mathit{pd}\to \{\mathit{pp}\}{}_{s}n$, where $\{\mathit{pp}\}{}_s$ is a fast proton pair emitted in forward direction with small excitation energy $E_{\mathit{pp}}<3$ MeV, has been studied at proton beam energies of $0.5–2.0$ GeV using the ANKE spectrometer at COSY-Jülich. The differential c.m. cross sections are measured in complete kinematics and provide angular distributions of the neutron emission angle in the range ${\theta }_n={168}^{°}$–${180}^{°}$, the dependence on beam energy at ${\theta }_n={180}^{°}$, angular distributions of the direction of the proton in the $\mathit{pp}$ rest frame, and distributions of the excitation energy $E_{\mathit{pp}}$ of the proton pair. The obtained data are analyzed on the basis of theoretical models previously developed for the $\mathit{pd}\to \mathit{dp}$ process in a similar kinematics and properly modified for the diproton channel in $\mathit{pd}\to \{\mathit{pp}\}{}_{s}n$. It is shown that the measured observables are highly sensitive to the short-range part of the nucleon-nucleon interaction.

The charmonium yields are expected to be considerably suppressed if a deconfined medium is formed in high-energy heavy-ion collisions. In addition, the bottomonium states, with the possible exception of the $\Upsilon (1S)$ state, are also expected to be suppressed in heavy-ion collisions. However, in proton-nucleus collisions the quarkonium production cross sections, even those of the $\Upsilon (1S)$, are also suppressed. These “cold nuclear matter” effects need to be accounted for before signals of the high-density QCD medium can be identified in the measurements made in nucleus-nucleus collisions. We identify two cold nuclear matter effects important for midrapidity quarkonium production: “nuclear absorption,” typically characterized as a final-state effect on the produced quarkonium state, and “shadowing,” the modification of the parton densities in nuclei relative to the nucleon, an initial-state effect. In this article, we characterize these effects and study the energy, rapidity, and impact-parameter dependence of initial-state shadowing.

Direct photon emission in heavy-ion collisions is calculated within a relativistic micro $+$ macro hybrid model and compared to the microscopic transport model, the Ultra-relativistic Quantum Molecular Dynamics model. In the hybrid approach, the high-density part of the evolution is replaced by an ideal three-dimensional hydrodynamic calculation. This allows the effects of viscosity and full local thermalization, in comparison with the transport model of the ideal fluid dynamics, to be examined. The origin of high-$p_{\perp }$ photons as well as the impact of elementary high-$\sqrt{s}$ collisions is studied. The contribution of different production channels and nonthermal radiation to the spectrum of direct photons is further explored. Detailed comparisons to the measurements by the WA98 Collaboration are also undertaken.

In the Israel-Stewart theory of dissipative hydrodynamics, the scaling properties of elliptic flow in $\mathrm{Au}+\mathrm{Au}$ collisions are studied. The initial energy density of the fluid was fixed to reproduce STAR data on $\varphi$-meson multiplicity in $0–5\%$ $\mathrm{Au}+\mathrm{Au}$ collisions such that, irrespective of fluid viscosity, entropy at the freeze-out is similar in ideal or in viscous evolution. The initial eccentricity or constituent quark number scaling is only approximate in ideal or minimally viscous ($\eta /s=1/4\pi$) fluid. Eccentricity scaling becomes nearly exact in more viscous fluid ($\eta /s⩾0.12$). However, in more viscous fluid, constituent quark number scaled elliptic flow for mesons and baryons splits into separate scaling functions. Simulated flows also do not exhibit “universal scaling”; that is, elliptic flow scaled by the constituent quark number and charged particles $v_2$ is not a single function of transverse kinetic energy scaled by the quark number. From a study of the violation of universal scaling, we obtain an estimate of quark-gluon plasma viscosity, $\eta /s=0.12\pm 0.03$. The error is statistical only. The systematic error in $\eta /s$ could be as large.

We extend the hadronic SU(3) nonlinear $\sigma$ model to include quark degrees of freedom. The choice of potential for the deconfinement order parameter as a function of temperature and chemical potential allows us to construct a realistic phase diagram from the analysis of the order parameters of the system. These parameters are the chiral condensate for the chiral symmetry restoration, and the scalar field $\Phi$ (as an effective field related to the Polyakov loop) for the deconfinement to quark matter. Besides reproducing lattice QCD results, for zero and low chemical potential, we are in agreement with neutron-star observations for zero temperature.

The neutron superfluidity in the inner crust of a neutron star has traditionally been studied considering either homogeneous neutron matter or a small number of nucleons confined inside the spherical Wigner-Seitz cell. Drawing analogies with the recently discovered multiband superconductors, we have solved the anisotropic multiband BCS gap equations with Bloch boundary conditions, thus providing a unified description taking consistently into account both the free neutrons and the nuclear clusters. Calculations have been carried out using the effective interaction underlying our recent Hartree-Fock-Bogoliubov nuclear mass model HFB-16. We have found that even though the presence of inhomogeneities lowers the neutron pairing gaps, the reduction is much less than that predicted by previous calculations using the Wigner-Seitz approximation. We have studied the disappearance of superfluidity with increasing temperature. As an application we have calculated the neutron specific heat, which is an important ingredient for modeling the thermal evolution of newly born neutron stars. This work provides a new scheme for realistic calculations of superfluidity in neutron-star crusts.

The interacting boson model (IBM) Hamiltonian is determined microscopically for general cases of low-lying quadrupole collectivity. Under the assumption that the multinucleon-induced surface deformations, which reflect nuclear forces and the Pauli principle, can be simulated by bosons, the interaction strengths of the IBM Hamiltonian are derived by mapping the potential energy surface of the mean-field model with Skyrme force onto the corresponding one of the IBM. These interaction strengths turn out to change gradually as functions of valence nucleon numbers. The energy eigenvalues and the wave functions are calculated with the exact treatment of the particle number and the angular momentum. We demonstrate how well the method works by taking Sm isotopes as an example, where a typical spherical-deformed shape-phase transition is reproduced successfully. We show that the physically relevant IBM interaction strengths can be determined unambiguously by the use of wavelet analysis. In addition, by the diagonalization of the boson Hamiltonian, quantum-mechanical correlation effects can be included in the eigenenergies, by which the basic properties of these nuclei are properly reproduced. The present method is applied to several other isotopic chains, Ba, Xe, Ru, Pd, W, and Os, in comparison to the experimental data. We point out the relevance of our results to the recently proposed critical-point symmetries. The predicted spectra and the $B(\mathrm{E}2)$ ratios are presented for heavy neutron-rich exotic nuclei in experimentally unexplored regions such as the right-lower corner of ${}^{208}\mathrm{Pb}$ on the nuclear chart.

We reanalyze the ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ inelastic scattering to the single $2_1^{+}$ and $3_1^{-}$ excitation channels at an incident energy of $E_{\mathrm{lab}}=1120$ MeV by a microscopic coupled-channel (CC) calculation with complex $G$-matrix interaction. The imaginary part of the folded potential is renormalized so as to reproduce the elastic angular distribution. It is found that the results of full CC calculations are still inconsistent with the experimental data for both $2_1^{+}$ and $3_1^{-}$ channels. It is also found that when the imaginary coupling terms are omitted, the calculated $2_1^{+}$-channel cross sections are improved, although the $3_1^{-}$-channel cross sections are slightly overestimated.

Isotope thermometry, widely used to measure the temperature of a hot nuclear system formed in energetic nuclear collisions, is examined in the light of the $S$-matrix approach to the nuclear equation of state of disassembled nuclear matter. Scattering between produced light fragment pairs, hitherto neglected, is seen to have an important bearing on extraction of the system temperature and volume at freeze-out from isotope thermometry. Taking due care with the scattering effects and decay of the primary fragments, a more reliable way to extract the nuclear thermodynamic parameters, by exploiting the least-squares fit to the observed fragment multiplicities, is suggested.

Effects of the density dependence of the nuclear symmetry energy on ground-state properties of superheavy nuclei are studied in the relativistic mean-field theory. It is found that the softening of the symmetry energy plays an important role in the empirical shift [Phys. Rev. C 67, 024309 (2003)] of spherical orbitals in superheavy nuclei. The calculation based on the relativistic mean-field models NL3 and FSUGold supports the double shell closure in ${}^{292}120$ with the softening of the symmetry energy. In addition, the significant effect of the density dependence of the symmetry energy on the neutron skin thickness in superheavy nuclei is investigated.