Speaker
Estanislao Aguayo
(P)
Description
The Majorana collaboration is searching for neutrinoless double beta decay using 76Ge, which
has been shown to have a number of advantages in terms of sensitivities and backgrounds. The
observation of neutrinoless double-beta decay would show that lepton number is violated and that
neutrinos are Majorana particles and would simultaneously provide information on neutrino mass.
Attaining sensitivities for neutrino masses in the inverted hierarchy region, 1550 meV, will require
large, tonne-scale detectors with extremely low backgrounds, at the level of 1 count t1 y1 or
lower in the region of the signal. The Majorana collaboration, with funding support from DOE
Oce of Nuclear Physics and NSF Particle Astrophysics, is constructing the Demonstrator, an
array consisting of 40 kg of p-type point-contact high-purity germanium (HPGe) detectors, of which
30 kg will be enriched to 86% in 76Ge. The Demonstrator is being constructed in a clean
room laboratory facility at the 4850' level (4160 m.w.e.) of the Sanford Underground Research
Facility (SURF) in Lead, SD. It utilizes a compact graded shield approach with the inner portion
consisting of ultra-clean Cu that is being electroformed and machined underground. The primary
aim of the Demonstrator is to show the feasibility of a future tonne-scale measurement in terms
of backgrounds and scalability.