Speaker
Dr
Peter C. Rowson
(SLAC (US))
Description
The EXO collaboration is searching for neutrinoless double beta decay in 136Xe. Observation of this process would establish the Majorana nature of neutrinos and lepton number violation, while determining an absolute mass scale for neutrinos. The EXO-200 detector is a ultra low background TPC, with an active mass of ~100 kg of liquid xenon enriched to 80.6% in the isotope 136. The detector is currently operating at the underground WIPP site in New Mexico, USA and has been collecting data since May 2011. The collaboration has previously reported the first observation of two-neutrino double beta decay in 136Xe. In our new data, no signal is observed for an exposure of 32.5 kg-yr, with a background of ∼1.5 × 10−3 kg−1 yr−1 keV−1 in the ±1 sigma region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T1/2(136Xe) > 1.6 × 1025 yr (90% CL), corresponding to effective Majorana masses of less than 140–380 meV, depending on the matrix element calculation. Current R&D efforts towards a ton-scale experiment will also be discussed.
Author
Dr
Peter C. Rowson
(SLAC (US))
