Exotic nuclear decay observed in dark-matter detector – physicsworld.com

An uncommon and extraordinarily uncommon nuclear decay that entails the simultaneous bring collectively shut of two atomic electrons by a xenon-124 nucleus has been seen in a heart-broken-matter detector. Physicists within the XENON Collaboration contain measured the half of-lifestyles of the two-neutrino double electron bring collectively shut direction of to be about 10²² years, which is ready a trillion conditions the age of the universe. Discovering out this uncommon decay could shed gentle on a linked direction of called neutrinoless double electron bring collectively shut, which if seen, would uncover critical files relating to the persona of the neutrino that goes past Long-established Mannequin of particle physics.

Electron bring collectively shut is a normal mode of nuclear decay that happens when an atomic electron interacts with a proton within the nucleus to label a neutron and an electron neutrino. Two-neutrino double electron bring collectively shut occurs when two electrons are captured directly and is a noteworthy rarer direction of. As successfully as offering critical files relating to the pattern of the nucleus, watching two-neutrino double electron bring collectively shut could attend physicists devise experiments to leer neutrinoless double electron bring collectively shut. This hypothetical direction of can solely happen if the neutrino is its bring collectively antiparticle, which is now not predicted by the Long-established Mannequin. As successfully as establishing the neutrino as the main traditional particle to be a Majorana fermion, detecting neutrinoless double electron bring collectively shut would supply critical files relating to the absolute mass of the neutrino.

Buried deep below Gran Sasso mountain in Italy, the XENON1T darkish matter detector comprises about 3 tonne of ultrapure liquid xenon. The experiment ran for one year in 2017-18 buying for hypothetical darkish-matter particles called WIMPS, that are anticipated to collide infrequently with xenon nuclei. Collisions would invent gentle and electrons, which is in a web roar to both be detected by the apparatus.

Auger electrons

While XENON1T has viewed no evidence for WIMPS, physicists contain been also on the ogle-out for X-rays and Auger electrons emitted from tellurium-124 atoms – that are produced when xenon-124 undergoes two-neutrino double electron bring collectively shut. The XENON group spotted 126 such occasions within the detector over the direction of a year. Even supposing xenon-124 makes up solely about 0.1% of the xenon within the detector, there may be unruffled a large desire of the nuclei uncover. Vivid the need of xenon-124 nuclei within the detector and the number that decayed in a year allowed the group to calculate the half of-lifestyles of two-neutrino double electron bring collectively shut to be 1.8×10²² years, which is the longest half of-lifestyles ever measured directly.

XENON1T is now being upgraded to label XENONnT, which will comprise 8 tonne of xenon and contain even lower background radiation levels. The XENON group dispute that their discovery “items the stage” for searches for neutrinoless double electron bring collectively shut and other uncommon decay processes the employ of XENONnT as successfully as two other upcoming detectors – LZ to be in-built the US and PandaX-4T in China.

The analysis is described in Nature.