Limits on the Existence of sub-MeV Sterile Neutrinos from the Decay of $^7$Be in Superconducting Quantum Sensors

TL;DR

This study uses superconducting quantum sensors to search for sub-MeV sterile neutrinos via $^7$Be decay, setting new exclusion limits that surpass previous constraints in the 100-850 keV mass range.

Contribution

It introduces a novel decay-momentum reconstruction method with superconducting sensors to improve sterile neutrino constraints.

Findings

Set new exclusion limits on sterile neutrinos in 100-850 keV range.

Demonstrated the effectiveness of superconducting tunnel junction sensors for neutrino searches.

Achieved an order of magnitude improvement over previous experimental limits.

Abstract

Sterile neutrinos are natural extensions to the standard model of particle physics and provide a possible portal to the dark sector. We report a new search for the existence of sub-MeV sterile neutrinos using the decay-momentum reconstruction technique in the decay of $^7$Be. The experiment measures the total energy of the $^7$Li daughter atom from the electron capture decay of $^7$Be implanted into sensitive superconducting tunnel junction (STJ) quantum sensors. This first experiment presents data from a single STJ operated at a low count rate for a net total of 28 days, and provides exclusion limits on sterile neutrinos in the mass range from 100 to 850 keV that improve upon previous work by up to an order of magnitude.