Physics of Particles and Nuclei最新文献

This paper presents an overview of the latest results and research methodology of statistical combination of Higgs invisible searches at ATLAS Large Hadron Collider experiment using data collected in Run I ((sqrt s ) = 7 TeV, 8 TeV) and Run II ((sqrt s ) = 13 TeV). In this search, multiple production modes of the Standard Model Higgs boson were considered. Obtained upper limit on H → inv branching ratio of 0.107 (0.077) at the 95% confidence level is observed (expected). This result is the most strict up to date. Obtained values at the ATLAS experiment are compared with the results of direct-search experiments.

The scheme of a plasma neutron generator on a plasma target, theoretical and applied aspects of modeling the magnetohydrodynamic flow of controlled plasma, substantiation of the discretization of condensed plasma and ion fluxes based on the introduction of the concept of flow discreteness stemming from the development of methods and technology for creating and forming electronically controlled ion and plasma fluxes in magnetic fields by grouping fluxes in certain sequences are briefly considered. The operation of the developed installations is based on the physical principles of discrete compaction of plasma and ion flows by changing the control parameters of magneto-optical systems. Preliminary experiments have been carried out on a setup with a plasma electric generator for irradiating semiconductor heterostructures to create radiation-induced defects.

In addition to the proton–proton (pp) chain consisting only of isotopes of hydrogen and helium fusion of hydrogen into helium occurs in stars through the carbon-nitrogen-oxygen (CNO) cycle, in which the nuclear synthesis is catalyzed by C, N, and O nuclei. The CNO cycle produces only 1% of all solar energy and it is secondary for the Sun. However, for more massive and hot stars this cycle is dominant. In 2020–2023 the international Borexino collaboration presented results on first detection of neutrinos emitted in CNO cycle reactions on the Sun. The research also obtained results on measuring the beta spectrum of ²¹⁰Bi, knowing which is necessary to register the signal from CNO neutrinos.

Calibration experiments with artificial neutrino sources ⁵¹Cr and ³⁷Ar in the gallium solar neutrino experiments SAGE and GALLEX showed a neutrino capture rate significantly lower than expected. This result, known as the gallium anomaly, was later confirmed at a significance level of more than 4σ in the BEST experiment on the UNU GGNT with a ⁵¹Cr source. For a detailed study of the gallium anomaly, the BEST-2 experiment on a gallium target with an artificial source of ⁵⁸Co is proposed.

A search for the processes of double beta decay of ⁸²Se into excited states of ⁸²Kr is conducted using the OBELIX setup. The measurements are conducted using a 600 cm³ HPGe detector. The detector is surrounded by 6.5 kg of enriched selenium (the content of ⁸²Se was ~92.5%). The data collected over 17 572.2 h of measurements are given. As a result, a world-record sensitivity is reached for transitions of this type. Specifically, we have found an indication of the existence of two-neutrino ⁸²Se decay into the first 0^{+ 82}Kr excited state with a half-life of (4.4_{{ - 0.9}}^{{ + 1.6}}) × 10²² years.

Compact accelerator-driven neutron sources (CAN) are a modern trend in the development of research techniques using neutrons. CAN is a low-power neutron sources operating on the basis of pulsed ion or electron accelerators. The article presents the development results of the compact neutron source project DARIA (Dedicated for Academic Research and Industrial Application) based on a linear resonant proton accelerator. The CAN DARIA is designed to provide the Russian Federation’s scientific community with a modern neutron sources network.

A universal elementary particle detector is developed for the SPD (Spin Physics Detector) experiment to be carried out using NICA (Nuclotron-based Ion Collider fAcility) collider. It is proposed to develop the FARICH (Focusing Aerogel RICH) counter as a specialized identification system. The concept of the FARICH counter for the SPD detector is outlined. The calculation results are discussed and conclusions on testing the prototype are given. Achievements in producing Cherenkov aerogel radiators in Novosibirsk are discussed.

The optical throughput of Imaging Atmospheric Cherenkov Telescopes (IACTs) is an important detector characteristic used to reconstruct the parameters of detected events. The TAIGA astrophysical complex includes TAIGA-IACT facility—an array of three IACTs and 120 TAIGA-HiSCORE wide-angle Cherenkov detectors on an area of 1 km². The complex is aimed at solving the relevant problems in gamma-astronomy of very high energies (VHE) and ultra high energies (UHE). The TAIGA-HiSCORE complex makes it possible to reconstruct the lateral distribution function (LDF) of Cherenkov photons in an extensive air shower (EAS). This information makes it possible to determine the number of Cherenkov photons reaching IACT reflectors and, eventually, to determine the efficiency of their detection. The present paper describes this approach to calibrating the optical throughput of the TAIGA-IACT facility.

The outer detector (OD) of the future next-generation water Cherenkov project Hyper-Kamiokande plays a crucial role in tagging and further reduction of the backgrounds. A PMT + WLS plate module is used as the photon detector element to increase the overall light collection efficiency. The R&D work on the WLS plates was conducted at the INR RAS laboratory: an optimisation of the chemical composition and the geometry of the plates, and the performance of the PMT + WLS plate modules was studied with a LED source as well as with the Cherenkov light. The results are summarised in the paper.

Since spring 2022, three atmospheric Cherenkov gamma-ray telescopes (AGT) have been operating as part of the TAIGA experiment at the MSU-ISU Astrophysical Complex in the Tunka Valley (Republic of Buryatia), and the fourth telescope will be soon commissioned. Such telescopes are the main instruments of ground-based high-energy gamma-ray astronomy, allowing events to be separated from gamma-quanta and events from charged particles of cosmic rays. The four existing telescopes are based on the design of the HEGRA telescopes, which were developed in the 1980s and are currently obsolete in terms of design solutions. The article presents an overview of the technical modernization of the fifth Cherenkov telescope. It shows the possibility of replacing certain components of the telescope with finished products manufactured in series, with specified quality indicators, warranty and assigned resources and service life. The changes introduced are also described not only for the mechanical part of the telescope, but also for its subsystems, in particular the mirror heating system and light-protective hoods.