Vol 46, No 3 (2019)

The detection of spectator nucleons emitted forward in the beam direction in experiments on the study of nucleus—nucleus interactions using forward Zero Degree Calorimeters (ZDCs) allows the determination of the event centrality and the detection of the nucleons from electromagnetic dissociation (EMD). In this paper, we propose a simple combinatorial model for calculating the energy releases in the ZDC, taking into account the calorimeter acceptance and efficiency. Using this model, the effect of the limited acceptance and nucleon detection efficiency on the spectral shape in the ZDC and the possibility of measuring the yield of a certain number of nucleons from the EMD is studied at LHC energies.

Single quantum wells in the Si_1-xGe_x/Si (x < 0.1) system grown in the mode of molecular Ge flow modulation in forming the solid solution layer are studied. The grown heterostructures are investigated by the low-temperature photoluminescence method, and their properties were compared with the properties of similar heterostructures grown without modulation of the Ge molecular flow. It is shown that modulation of the Ge flow has almost no effect on the spectral properties of the quantum wells.

A new model of the formation of primordial black holes (PBHs) is considered. The PBH generation mechanism is based on the collapse of massive walls formed in a scalar field during second-order phase transitions caused by quantum fluctuations during inflation. An essential feature of the mechanism is the formation of primordial black holes in the form of clusters. An analytical spectrum of PBH masses is obtained. We also demonstrate the possibility of forming the clusters with a total mass of ∼ 10⁵–10⁸M_☉, ∼ 1 pc in size, and ∼ 10¹¹ in number, which corresponds to the observational data on the number of galaxies in the visible region of the Universe. The prospect for the use of the proposed approach as a new scenario of the formation of galactic nuclei in the early Universe is shown.

The results of measurements of the exclusive cross section for the e⁺e⁻ → D^(*)±D^*∓ process near the open charm threshold with initial-state radiation are presented. The analysis is based on the experimental data collected with the Belle detector at energies \(\sqrt s \) equal to ϒ(4S), ϒ(5S) production energies, and energies of the nearby continuum corresponding to an integrated luminosity of 951 fb⁻¹. The accuracy of the measurements of the cross sections is twice higher in comparison with the previous results of the Belle collaboration. An angular analysis is performed for the final state D*⁺D*⁻ for the first time with the result that the cross section is decomposed into three components corresponding to the possible combinations of D*-meson polarizations in the final state.