Approximate analytical solutions of a Duffin-Kemmer-Petiau (DKP) equation are obtained via an elegant ansatz after successive transformations. Apart from the wide application of the DKP equation in both cosmology and theoretical nuclear physics as well as the physical significance of the Coulomb interaction, this is particularly important as we have provided a solution to the corresponding Heun equation.

The cross sections of $B_c$ absorption by $\rho$ mesons are calculated using a meson-exchange model based on a hadronic Lagrangian having SU(5) symmetry. Calculated cross sections are found to be in the ranges 0.6–3 and 0.05–0.3 mb for the processes $B_c^{+}\rho \to D^{*}B$ and $B_c^{+}\rho \to D{B}^{*}$, respectively, when the monopole form factor is included. The total $B_c$ absorption cross section by $\rho$ mesons is found to be about three times smaller than the calculated total cross section by pions using the same model. These results could be useful in calculating the production rate of $B_c$ mesons in relativistic heavy-ion collisions.

We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new “constituent quark model” sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition, we extract the $\alpha =0$ pole contribution for both proton and nuclei. Using the modern high-energy proton data, we find that the $\alpha =0$ pole contribution differs significantly from the Thomson term, in contrast with the original findings by Damashek and Gilman.

Initial states of “glasma” in high-energy heavy-ion collisions are longitudinal classical color electric and magnetic fields. Assuming finite color electric conductivity, we show that the color electric field decays by quark pair production with the lifetime of the order of $Q_s^{-1}$, i.e., the inverse of the saturation momentum. Quarks and antiquarks created in the pair production are immediately thermalized as long as their temperature ${\beta }^{-1}$ is lower than $Q_s$. Namely, the relaxation time of the quarks to be thermalized is much shorter than $Q_s^{-1}$ when ${\beta }^{-1}\ll Q_s$. We also show that the quarks acquire longitudinal momentum of the order of $Q_s$ by the acceleration of the electric field. To discuss the quark pair production, we use chiral anomaly, which has been shown to be a very powerful tool in the presence of strong magnetic field.

Bulk fermionic matter, as can be notably found in supernova matter and neutrons stars, is subject to correlations of infinite range due to the antisymmetrization of the $N$-body wave function, which cannot be explicitly accounted for in a practical simulation. This problem is usually addressed in condensed matter physics by means of the so-called twist averaged boundary condition method. A different ansatz based on the localized Wannier representation has been proposed in the context of antisymmetrized molecular dynamics. In this paper we work out the formal relation between the two approaches. We show that, while the two coincide when working with exact eigenstates of the $N$-body Hamiltonian, differences appear in the case of variational approaches, which are currently used for the description of stellar matter. Some model applications with fermionic molecular dynamics are shown.

High-precision measurements of $\langle 0_1\left|\right|M\left(E2\right)\left|\right|2_1\rangle$ matrix elements from the Coulomb excitation of ${}^{124,126,128}$Sn on a ${}^{12}$C target are presented. The extracted $B\left(E2\right)$ values decrease monotonically from the neutron midshell toward the ${}^{132}$Sn double-shell closure, despite a near constancy in the first $2^{+}$ level energy. Furthermore, Coulomb excitation of ${}^{124,126,128}$Sn on an enriched ${}^{50}$Ti target, combined with the results from the ${}^{12}$C target, provide a measure of the static quadrupole moments, $Q\left(2_1{}^{+}\right)$ (expected to be zero for a spherical shape). These new results confirm that the unstable neutron-rich ${}^{126,128}$Sn isotopes have deformations consistent with zero. The present study marks the first report on measured $2_1{}^{+}$ static quadrupole moments for unstable closed-shell nuclei.

We study shear viscosities of different species in hot and neutrino-trapped dense matter relevant to protoneutron stars. It is found that the shear viscosities of neutrons, protons and electrons in neutrino-trapped matter are of the same orders of magnitude as the corresponding shear viscosities in neutrino-free matter. Above all, the shear viscosity owing to neutrinos is higher by several orders of magnitude than that of other species in neutrino-trapped matter. Next we investigate the effect of shear viscosity, in particular, neutrino shear viscosity, on the thermal nucleation rate of droplets of antikaon condensed matter in protoneutron stars. The first-order phase transition from hadronic matter to antikaon condensed matter is driven by the thermal nucleation process. We compute the equation of state used for the calculation of shear viscosity and thermal nucleation time within the relativistic mean-field model. Neutrino shear viscosity enhances the prefactor in the nucleation rate by several orders of magnitude compared with the $T^4$ approximation of earlier calculations. Consequently the thermal nucleation time in the $T^4$ approximation overestimates our result. Furthermore, the thermal nucleation of an antikaon droplet might be possible in neutrino-trapped matter before neutrino diffusion takes place.

The Rankine-Hugoniot condition has been solved to study phase transition in an astrophysical scenario mainly in the case of phase transition from a neutron star (NS) to a quark star (QS). The equations of state and temperature play a huge role in determining the nature of the front propagation, which brings about the phase transition in a NS. The shock jump conditions can be solved analytically, but the situation changes drastically by the inclusion of the magnetic field. High magnetic fields, which are always associated with a NS play a huge role in determining the structure and evolution of a NS. So, a magnetic field has been introduced in the shock jump condition in the de Hoffmann-Teller frame. The modified conservation condition for the perpendicular and oblique shocks is obtained in this frame. Numerical solution of the perpendicular shock has been obtained, which shows considerable deviation from the nonmagnetic case. The results show that the magnetic field helps in shock generation. It also indirectly hints at the instability of the matter and thereby the NS for very high magnetic field, implying that NSs can only support a magnetic field of some finite strength.

An ab initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly magic and semimagic nuclei employing state-of-the-art microscopic nuclear interactions and explicitly treating pairing correlations through the breaking of U(1) symmetry associated with particle number conservation. The present paper introduces the formalism necessary to undertake applications at (self-consistent) second order using two-nucleon interactions in a detailed and self-contained fashion. First applications of such a scheme will be reported soon in a forthcoming publication. Future works will extend the present scheme to include three-nucleon interactions and implement more advanced truncation schemes.

The ${}^{12}$C nucleus is investigated in a nonmicroscopic $\alpha$-particle model involving local and nonlocal potentials. Faddeev equations formulated in configuration space are used to solve the three-body problem for bound and resonant states. We demonstrate that the nonlocal potential developed by Papp and Moszkowski [Mod. Phys. Lett. B 22, 2201 (2008)] appears to be particularly well adapted to study 3$\alpha$ clustering. We point out ${}^{12}$C states of positive-parity which share common features with the $0_2^{+}$ Hoyle states. Several negative-parity states revealing a clear bosonic $\alpha$-particle structure are also obtained.

Excited states in the $N=Z-2$ nucleus ${}^{44}$V have been observed for the first time. The states have been identified through particle-$\gamma$-$\gamma$ coincidence relationships and comparison with analog states in the mirror nucleus ${}^{44}$Sc. Mirror energy differences have been extracted and compared to state-of-the-art shell-model calculations which include charge-symmetry-breaking forces. Observed decay pattern asymmetries between the mirror pair are discussed in terms of core excitations, electromagnetic spin-orbit effects and isospin mixing.

We investigate the $\alpha +d$ elastic scattering and the radiative capture reaction of ${}^2$H(${\alpha ,\gamma )}^6$Li based on the $\alpha$ + $p$ + $n$ three-body model. The $\alpha +d$ scattering states are described by using the complex-scaled solutions of the Lippmann-Schwinger equation. We calculate the elastic phase shifts for the $\alpha +d$ scattering and the radiative capture cross section of ${}^6$Li. We evaluate the contributions of the $\alpha$ + $p$ + $n$ structures in those observables. It is found that in the $\alpha +d$ scattering process, the deuteron breakup and the rearrangement to the ${}^5$He $+$ $p$ and ${}^5$Li $+$ $n$ channels play prominent roles in reproducing the observed phase shifts and radiative capture cross section.

For ${}^6$Li scattering from ${}^{12}$C at five laboratory energies from 90 to 318 MeV, we study the dynamic polarization potential, DPP, due to the breakup of the projectile. The breakup is evaluated using standard continuum discretized coupled-channels formalism applied to a two-body cluster model of the projectile. The DPP is evaluated over a wide radial range using both direct $S$-matrix-to-potential inversion and trivially equivalent local potential methods which yield substantially and systematically different results. The radius at which the real DPP changes from external repulsion to interior attraction varies systematically with energy. This should be experimentally testable because, according to notch tests, this crossover radius is within a radial range to which elastic scattering should be sensitive. The imaginary DPP has an emissive (generative) region at the lower energies; this may be associated with counterintuitive properties of $|S_L|$.

Nuclide production cross sections measured at the Institute for Theoretical and Experimental Physics (ITEP) for the targets of ${}^{\mathrm{nat}}$Cr, ${}^{56}$Fe, ${}^{\mathrm{nat}}$Ni, ${}^{93}$Nb, ${}^{181}$Ta, ${}^{\mathrm{nat}}$W, ${}^{\mathrm{nat}}$Pb, and ${}^{209}$Bi irradiated by protons with energies from 40 to 2600 MeV were used to estimate the predictive accuracy of several popular high-energy transport codes. A general agreement of the ITEP data with the data obtained by other groups, including the numerous GSI data measured by the inverse kinematics method was found. Simulations of the measured data were performed with the mcnpx (bertini and isabel options), cem03.02, incl4.2 + abla, incl4.5 + abla07, phits, and cascade.07 codes. Deviation factors between the calculated and experimental cross sections have been estimated for each target and for the whole energy range covered by our measurements. Two-dimensional diagrams of deviation factor values were produced for estimating the predictive power of every code for intermediate, not measured masses of nuclei targets and bombarding energies of protons. Further improvements of all tested here codes are recommended. In addition, new measurements at ITEP of nuclide yields from the ${}^{208}$Pb target irradiated by 500-MeV protons are presented. A good agreement between these new data and the GSI measurements obtained by the inverse kinematics method was found.

Fusion data for ${}^{13}$C+${}^{13}$C, ${}^{12}$C+${}^{13}$C, and ${}^{12}$C+${}^{12}$C are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. The fusion is determined by ingoing-wave-boundary conditions (IWBC) that are imposed at the minimum of the pocket in the entrance channel potential. Quadrupole and octupole transitions to low-lying states in projectile and target are included in the calculations, as well as mutual excitations of these states. The effect of one-neutron transfer is also considered but the effect is small in the measured energy regime. It is shown that mutual excitations to high-lying states play a very important role in developing a comprehensive and consistent description of the measurements. Thus, the shapes of the calculated cross sections for ${}^{12}$C+${}^{13}$C and ${}^{13}$C+${}^{13}$C are in good agreement with the data. The fusion cross sections for ${}^{12}$C+${}^{12}$C determined by the IWBC are generally larger than the measured cross sections but they are consistent with the maxima of some of the observed peak cross sections. They are therefore expected to provide an upper limit for the extrapolation into the low-energy regime of interest to astrophysics.

A microscopic calculation of reaction cross sections for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for ${}^{40,48}$Ca, ${}^{58}$Ni, ${}^{90}$Zr, and ${}^{144}$Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agree very well with experimental data and predictions of a state-of-the-art fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. The effect of resonances from higher-order channels was assessed. Elastic angular distributions were also calculated within the same method, achieving good agreement with experimental data. Observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 70 MeV, with consistent angular distribution results.

Earlier we reported theoretical studies on the probable production of astatine radionuclides from ${}^{6,7}$Li- and ${}^9$Be-induced reactions on natural lead and thallium targets, respectively. The production of astatine radionuclides were investigated experimentally with two heavy-ion-induced reactions: ${}^9$Be $+$ ${}^{\mathrm{nat}}$Tl and ${}^7$Li $+$ ${}^{\mathrm{nat}}$Pb. Formation cross sections of the evaporation residues, ${}^{207,208,209,210}$At, produced in the (HI,$xn$) channel, were measured by the stacked-foil technique followed by off-line $\gamma$ spectrometry at low incident energies ($<$50 MeV). Measured excitation functions were interpreted in terms of a compound nuclear reaction mechanism using Weisskopf-Ewing and Hauser-Feshbach models. Measured cross-section values are lower than the respective theoretical predictions.

We present a study of the elliptic ($v_2$) and triangular ($v_3$) flow and their corresponding eccentricity fluctuations for asymmetric (Au+Ag, Au+Cu, and Au+Si) collisions at $\sqrt{s_{NN}}$ $=$ 200 GeV. These are compared to the corresponding results from symmetric (Au+Au and Cu+Cu) collisions at the same energy. The study which is carried out using a multiphase transport (AMPT) model shows that triangularity (${\epsilon }_3$), fluctuations in triangularity and $v_3$ do not show much variation for the different colliding ion sizes studied. However the eccentricity (${\epsilon }_2$), fluctuations in eccentricity and $v_2$, shows a strong dependence on colliding ion size for a given number of participating nucleons. Our study thus indicates that asymmetric heavy-ion collisions could be used to constrain models dealing with flow fluctuations in heavy-ion collisions.

One contribution to the energy loss of hard partons propagating through a medium as created in ultrarelativistic heavy-ion ($A$-$A$) collisions are elastic scattering processes with medium constituents. The magnitude of this energy loss contribution depends crucially on the effective mass of the medium constituents—in the limit of nonrecoiling static scattering centers, elastic energy loss vanishes. Thus, it is important to constrain the amount of elastic energy loss in order to gain information about the nature of the degrees of freedom in the medium as resolved by a hard parton. So far, the relative fraction of elastic (or rather incoherent) energy loss has been constrained from above by using path-length dependent observables. However, using the observation that subleading gluon energy dissipation into the medium is probed by some observables, such as hard dihadron correlations or the dijet asymmetry, a constraint from below can also be found. In this work, this idea is worked out within the in-medium shower evolution Monte Carlo (MC) code YaJEM-D.