Search for Neutrinoless Double-Beta Decay in $^{136}$Xe with EXO-200

TL;DR

This paper reports a search for neutrinoless double-beta decay in xenon-136 using the EXO-200 detector, setting new lower limits on the decay half-life and constraining neutrino mass parameters.

Contribution

First search for neutrinoless double-beta decay in $^{136}$Xe with EXO-200, establishing new half-life lower bounds and neutrino mass constraints.

Findings

No signal observed in 32.5 kg-yr exposure.

Lower limit on half-life: > 1.6 x 10^{25} years.

Effective Majorana mass constrained to less than 140-380 meV.

Abstract

We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1\sigma$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0\nu\beta\beta}$($^{136}$Xe) > 1.6 x 10$^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.