Electron-positron vacuum instability in strong electric fields. Relativistic semiclassical approach

The instability of electron-positron vacuum in strong electric fields is studied. First, falling to the Coulomb center is discussed at Z>137/2 for a spinless boson and at Z>137 for electron. Subsequently, focus is concentrated on description of deep electron levels and spontaneous positron production in the field of a finite-size nucleus with the charge Z>Zcr≃170. Next, these effects are studied in application to the low-energy heavy-ion collisions. Subsequently, we consider phenomenon of “electron condensation” on levels of upper continuum crossed the boundary of the lower continuum ϵ=−m in the field of a supercharged nucleus with Z≫Zcr. Finally, attention is focused on many-particle problems of polarization of the quantum electrodynamics (QED) vacuum and electron condensation at ultra-short distances from a source of charge. We argue for a principal difference of cases, when the size of the source is larger than the pole size rpole, at which the dielectric permittivity of the vacuum reaches zero and smaller rpole. Some arguments are presented in favor of the logical consistency of QED. All of the problems are considered within the same relativistic semiclassical approach

New large-volume detector at the Baksan Neutrino Observatory: Detector prototype

At the Baksan Neutrino Observatory (Institute for Nuclear Research of the Russian Academy of Sciences, Moscow) deployed in the Caucasus mountains, it is proposed to create, at a depth corresponding to about 4700 mwe (meter water equivalent), a large-volume neutrino detector on the basis of a liquid scintillator with a target mass of 10 kt. This article describes the current state of the first stage of the project, namely a prototype detector with a scintillator mass of 0.5 t. The design of the detector, the equipment and methods used are described

Vector Finder—A Toolkit for Track Finding in the MPD Experiment

A track reconstruction method based on a constrained combinatorial search for track candidates, i.e. combinations of detector hits possibly belonging to a track, is presented. The algorithm has been implemented as a Vector Finder software toolkit containing a track reconstruction procedure and tools to determine hit acceptance windows (a priori constraints) for the track search. Track reconstruction results for high multiplicity simulated events (∼1000 particles in the detector acceptance) are shown demonstrating good performance of the approach proposed

On the two-loop divergences in 6D, N=(1,1){\cal N}=(1,1) SYM theory

We continue studying $6D, {\cal N}=(1,1)$ supersymmetric Yang-Mills (SYM) theory in the ${\cal N}=(1,0)$ harmonic superspace formulation. Using the superfield background field method we explore the two-loop divergencies of the effective action in the gauge multiplet sector. It is explicitly demonstrated that among four two-loop background-field dependent supergraphs contributing to the effective action, only one diverges off shell. It is also shown that the divergences are proportional to the superfield classical equations of motion and hence vanish on shell

Properties of the QGP created in heavy-ion collisions

We review the properties of the strongly interacting quark-gluon plasma (QGP) at finite temperature $T$ and baryon chemical potential $\mu_B$ as created in heavy-ion collisions at ultrarelativistic energies. The description of the strongly interacting (non-perturbative) QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature $T_C$ from lattice QCD. Based on a microscopic transport description of heavy-ion collisions we discuss which observables are sensitive to the QGP creation and its properties

Electroweak Physics from the CMS Experiment at the LHC

The results obtained in the CMS experiment at the Large Hadron Collider (LHC) by studying electroweak interaction are surveyed

Scalar isoscalar mesons and the scalar glueball from radiative J/ψJ/\psi decays

A coupled-channel analysis of BESIII data on radiative J/ψ decays into ππ , KK¯ , ηη and ωϕ has been performed. The partial-wave amplitude is constrained by a large number of further data. The analysis finds ten isoscalar scalar mesons. Their masses, widths and decay modes are determined. The scalar mesons are interpreted as mainly SU(3)-singlet and mainly octet states. Octet isoscalar scalar states are observed with significant yields only in the 1500-2100 MeV mass region. Singlet scalar mesons are produced over a wide mass range but their yield peaks in the same mass region. The peak is interpreted as scalar glueball. Its mass and width are determined to M=1865 ±25 −30+10 MeV and Γ=370 ± 50−20+30 MeV, its yield in radiative J/ψ decays to ( 5.8±1.0)10−3

Concept of Coherence in Neutrino and Antineutrino Scattering off Nuclei

The concept of coherence in the scattering of neutrinos and antineutrinos off nuclei is discussed. Motivated by the results of the COHERENT experiment, a new approach to coherence in these processes is proposed, which allows a unified description of the elastic (coherent) and inelastic (incoherent) contributions to the total cross section for neutrino and antineutrino scattering off nuclei at energies below 100 MeV. Experiments and physical problems for coherent scattering of (anti)neutrinos off nuclei are briefly discussed. The extended appendix covers the main points and conclusions of the proposed approach in pedagogical detail