| Abstract: Neutrinos, the only neutral elementary fermions, have provided many surprises. Flavor
oscillations reveal the non-conservation of the lepton flavor number and demonstrate that
neutrino masses are finite; yet they are surprisingly much smaller than those of other fermions
(by at least six orders of magnitude!) It is then natural to ask if the mechanism providing the
mass to neutrinos is the same that gives masses to the other (charged) elementary fermions
and if neutrinos are described by 4-component Dirac wavefunctions or, as is possible for neutral
particles, by 2-component Majorana ones.
The hypothetical phenomenon of neutrino-less double-beta decay can probe the Majorana
nature of neutrinos and the conservation of the total lepton number. It may also help
elucidating the origins of mass in the neutrino sector. This is the Frontier of neutrino physics.
Following the well-known principle that there is no free lunch in life, interesting half-lives for
neutrino-less double-beta decay exceed 10^{25} years (or ~10^{15} times the age of the Universe!)
making experiments rather challenging. I will describe nEXO, a 5-tonne, enriched Xenon
experiment with a sensitivity reaching beyond 10^{28} years, or >100 times the current state of the
art. The nEXO detector derives directly from EXO-200, a very successful, rogue detector built
by a collaboration with a heavy SLAC-Stanford participation. Link to the Event Video |