Status and Results from the EXO Collaboration

Abstract

The Enriched Xenon Observatory (EXO) is an experimental program search- ing for neutrinoless double-beta decay using 136 Xe. Such a search can shed light on the Majorana nature of the neutrino (whether the neutrino is its own anti-particle), the ab- solute mass scale of neutrinos, and beyond standard model processes that violate lepton number conservation. The first phase of the experiment, EXO-200, uses 200 kg of xenon with 80% enrichment in 136 Xe in a single-phase liquid xenon time projection chamber (TPC). The double-beta decay of xenon is detected in the ultra-low background TPC by collecting both the scintillation light and the ionization charge. The detector has been tak- ing low background physics data with enriched xenon at the Waste Isolation Pilot Plant (WIPP) in New Mexico since early May 2011. The results produced from the collab- oration include the first observation of two-neutrino double-beta decay of 136 Xe, and a neutrinoless double-beta decay search result that places one of the most stringent limits on the e ective Majorana neutrino mass. Building on the success of EXO-200, the col- laboration is performing feasibility studies and R&D work for a future multi-tonne scale experiment named nEXO. During the talk, I will discuss the latest results from EXO-200 and prospects of neutrinoless double-beta decay search with both EXO-200 and nEXO.