Status of EXO-200

TL;DR

EXO-200 is a liquid xenon time projection chamber designed to search for neutrinoless double beta decay in 136Xe, aiming to measure neutrino properties with high sensitivity and low background noise.

Contribution

It introduces a novel ultra-low background TPC with combined scintillation and ionization detection for neutrinoless double beta decay search.

Findings

Projected sensitivity to half-life of 6.4×10^25 years

First measurement of two-neutrino mode in 136Xe

Effective Majorana neutrino mass range of 0.13-0.19 eV

Abstract

EXO-200 is the first phase of the Enriched Xenon Observatory (EXO) experiment, which searches for neutrinoless double beta decay in 136Xe to measure the mass and probe the Majorana nature of the neutrino. EXO-200 consists of 200 kg of liquid Xe enriched to 80% in 136Xe in an ultra-low background TPC. Energy resolution is enhanced through the simultaneous collection of scintillation light using Large Area Avalanche Photodiodes (LAAPD's) and ionization charge. It is being installed at the WIPP site in New Mexico, which provides a 2000 meter water-equivalent overburden. EXO-200 will begin taking data in 2009, with the expected two-year sensitivity to the half-life for neutrinoless double beta decay of 6.4 10^25 years. According to the most recent nuclear matrix element calculations, this corresponds to an effective Majorana neutrino mass of 0.13 to 0.19 eV. It will also measure the two neutrino mode for the first time in 136Xe.