NUCLEAR DOUBLE BETA DECAY,FUNDAMENTAL PARTICLE PHYSICS,HOT DARK MATTER, AND DARK ENERGY

摘要

Nuclear double beta decay, an extremely rare radioactive decay process, is - in one of its variants - one of the most exciting means of research into particle physics beyond the standard model. The large progress in sensitivity of exper-iments searching for neutrinoless double beta decay in the last two decades -based largely on the use of large amounts of enriched source material in "active source experiments" - has lead to the observation of the occurrence of this pro-cess in nature (On a 6.4 sigma level), with the largest half-life ever observed for a nuclear decay process (2.2x 10~(25) y). This has fundamental consequences for particle physics - violation of lepton number, Majorana nature of the neutrino. These results are independent of any information on nuclear matrix elements (NME) *. It further leads to sharp restrictions for SUSY theories, sneutrino mass, right-handed W-boson mass, superheavy neutrino masses, composite-ness, leptoquarks, violation of Lorentz invariance and equivalence principle in the neutrino sector. The masses of light-neutrinos are found to be degenerate, and to be at least 0.22±0.02 eV. This fixes the contribution of neutrinos as hot dark matter to >4.7% of the total observed dark matter. The neutrino mass determined might solve also the dark energy puzzle.