Neutrino hunt starts with nothing
Test runs of one of the world’s most advanced sensors have found nothing – exactly what they were looking for.
The Germanium Detector Array (GERDA) is built to detect a particular neutrino decay process which, if it exists, would prove that neutrinos are indistinguishable from their antiparticles.
It is part of a mind-bending effort to detect something that would prove our Universe is dominated by matter rather than antimatter.
The latest experiment at GERDA failed to find the neutrino decay, but being able to detect no background signal at all means that future searches will be highly sensitive to picking up the decay.
Certain extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in the Universe by assuming that neutrinos are their own antiparticles.
If this holds true, then a form of radioactive decay called neutrinoless double-beta decay - in which an atomic nucleus decays and emits two electrons and no neutrinos - should exist.
However, because the half-life for neutrinoless double-beta decay is at least 15 orders of magnitude longer than the age of the Universe, its observation would require the suppression of all background signals that may interfere.
The GERDA (GERmanium Detector Array) Collaboration has reported the first data from Phase II of the GERDA experiment, in which they have searched for neutrinoless double-beta decay in 35.6 kilograms of the isotope 76Ge.
By using a system that vetoes background events, the authors report that they have achieved the first background-free experiment in the field. However, they have found no hint of neutrinoless double-beta decay.
The background-free result is “a remarkable achievement for the field, suggesting that future searches will be highly sensitive to neutrinoless double-beta decay,” according to researcher Phillip Barbeau.