abstract

We consider the phenomenon of the Andreev reflection of “hadrons” at the interface between hadronic and color superconducting phases, which are expected to appear in the neutron star interior. Here, hadrons are defined as a superposition of constituent quarks, each of which is Andreev-reflected. We study, at the qualitative level, what kind of reflections are possible to come out of incident mesons and baryons in the hadronic phase, attached to different color superconducting phases. Then, some peculiar patterns of the reflections are obtained.

abstract

The cross sections of \(e^+e^- \rightarrow \pi Z_c(3900) \rightarrow \pi \pi J/\psi \) and \(e^+e^- \rightarrow \pi Z_c(3900) \rightarrow \pi D\bar {D}^{*}\) have been measured by the BESIII experiment. We try to perform a combined fit to the cross sections with one Breit–Wigner function, the fit results show the structure’s mass and width \(M=(4232\pm 5)\) MeV/\(c^2\), \({\mit \Gamma }=(65\pm 21)\) MeV. The ratio \(\frac {\mathcal {B}(Z_c(3900)\rightarrow D\bar {D}^{*})}{\mathcal {B}(Z_c(3900)\rightarrow \pi J/\psi )}\) is determined to be \((16\pm 6)\). We also try to fit the cross sections with two Breit–Wigner functions, while we cannot come to any definitive conclusions about the second structure. More measurements are desired to improve the understanding of \(e^+e^- \rightarrow \pi Z_c(3900)\) line shape.

abstract

For the first time, a systematic calculation of low-energy proton–nucleus elastic scattering off a series of doubly closed-shell nuclei is carried out. The direct and exchange elements of the Coulomb interaction between protons have been included to the residual interaction of the particle-vibration coupling (PVC). The nucleon–nucleon (\(NN\)) effective interaction of the Skyrme-type is consistently used in the whole process to generate the microscopic optical potential (MOP). Within the present microscopic optical potential model, angular distributions and analyzing power could be reproduced without any adjustable parameters.

abstract

The energy spectra of numerous radioactive samples placed on a rotating disk can be measured with a single-gamma radiation detector. This technique provides also lifetime information when the same sample returns several times close to the radiation detector. However, the presence of neighboring sources may affect the primary measurement. Assuming equal activity of all sources, analytical formulas for the relative contribution of neighboring sources are developed for typical configurations of 2, 3, 4, 6, 8, 12, 16 samples on the rotating disk. The calculated values compare well to the experimental results obtained for the configuration of 16 samples. The resulting analytical formulas help to decid, whether a passive shield around the detector is needed to reduce the contribution from neighboring samples, prior to the precise Monte Carlo simulation of the experimental set-up.

abstract

Complete angular distributions including both forward and backward angles are reported for the reaction \(\mathrm {^{13}C(^{11}B}\), \(\mathrm {^{12}C)^{12}B}\) at \(E_\mathrm {lab}\)(\(\mathrm {^{11}B})=45\) MeV leading to the ground and excited states of \(^{12}\)C and \(^{12}\)B. This reaction explores the interplay of proton and neutron transfers as well of those for larger clusters. The experimental data were analyzed within the coupled-reaction-channels method (CRC) that included the \(\mathrm {^{13}C} + \mathrm {^{11}B}\) elastic scattering channel as well as channels for one- and two-step transfers of nucleons in the coupling scheme. The necessary \(\mathrm {^{13}C} + \mathrm {^{11}B}\) optical potential parameters were obtained from previous work, while those for \(\mathrm {^{12}C} + \mathrm {^{12}B}\) were deduced from fitting the calculations to the \(\mathrm {^{13}C(^{11}B}, \mathrm {^{12}C)^{12}B}\) reaction data. Needed spectroscopic amplitudes of transferred nucleons and clusters were calculated within the translational-invariant shell model (TISM). The data are well-described by proton transfers while contributions from neutron transfer are only important at the largest angles. New global optical potentials for the elastic scattering of \(^{8,10,11}\)B isotopes were tested and found to describe the forward angles reaction data but not those for the middle and larger angles even when the ground-state reorientation of \(\mathrm {^{11}B}\) in the entrance channel is included.

abstract

We investigate the non-Langevin relative of the Lévy-driven Langevin random system, under an assumption that both systems share a common (asymptotic, stationary, steady-state) target pdf. The relaxation to equilibrium in the fractional Langevin–Fokker–Planck scenario results from an impact of confining conservative force fields on the random motion. A non-Langevin alternative has a built-in direct response of jump intensities to energy (potential) landscapes in which the process takes place. We revisit the problem of Lévy flights in superharmonic potential wells, with a focus on the extremally steep well regime, and address the issue of its (spectral) “closeness” to the Lévy jump-type process confined in a finite enclosure with impenetrable (in particular reflecting) boundaries. The pertinent random system “in a box/interval” might be expected to have a fractional Laplacian with suitable boundary conditions as a legitimate motion generator. It is not the case. Another problem is that, in contrast to Dirichlet boundary problems, a concept of reflecting boundary conditions and the path-wise implementation of the pertinent random process in the vicinity, or sharply at reflecting boundaries, are not unequivocally settled for Lévy processes. This ambiguity extends to non-local analogs of Neumann conditions for fractional generators, which do not comply with the traditional path-wise picture of reflection at the impenetrable boundary.