Fundamental interactions involving neutrons and neutrinos: reactor-based studies led by the Petersburg Nuclear Physics Institute (National Research Center "Kurchatov Institute") [PNPI (NRC KI)]
The National Research Center "Kurchatov Institute", Konstantinov Petersburg Nuclear Physics Institute, Orlova Roshcha, Gatchina, Leningradskaya Region, 188300, Russian Federation
Neutrons of very low energy (∼ 10−7 eV), commonly known as ultracold, are unique in that they can be stored in material and magnetic traps, thus enhancing methodical opportunities for conducting precision experiments and probing the fundamentals of physics. One of the central problems of physics, of direct relevance to the formation of the Universe, is the violation of time invariance. Experiments searching for the nonzero neutron electric dipole moment serve as a time invariance test, and the use of ultracold neutrons provides very high measurement precision. Precision neutron lifetime measurements using ultracold neutrons are extremely important for checking ideas on the early formation of the Universe. This paper discusses problems that arise in studies using ultracold neutrons. Also discussed are the currently highly topical problem of sterile neutrinos and the search for reactor antineutrino oscillations at distances of 6—12 meters from the active zone. The field reviewed is being investigated at multiple facilities globally. The present paper mainly concentrates on the PNPI-led studies on WWR-M PNPI (Gatchina), ILL (Grenoble), and SM-3 (Dimitrovgrad) reactors and also covers the results of the preparatory work at PNPI for the construction of the PIK reactor.