Astroparticle Seminar

Observation of Two-Neutrino Double-Beta Decay in ¹³⁶Xe:
First EXO Results in the Search for the Neutrino-less decay

Jacques A. Farine

Laurentian University

The Enriched Xenon Observatory (EXO) collaboration has observed the two-neutrino double beta decay of ¹³⁶Xe with EXO-200, a prototype to the EXO detector in development. This second order process, predicted by the Standard Model, has been observed for several nuclei but not for ¹³⁶Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrino-less double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale.

The EXO-200 detector and underground site at WIPP, New Mexico, will be presented, and the observation of the two-neutrino decay discussed. The experimental efforts in the filed will be highlighted, with comments on the calculations of nuclear matrix elements. The development of EXO will be discussed: a multi-tonne detector with daugther ion identification as a powerful background suppression tool, with SNOLAB a possible site.