46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015;
Columbus, Ohio
Session G2: Interface with Particle and Nuclear Physics
8:00 AM–10:00 AM,
Wednesday, June 10, 2015
Room: Union ABC
Co-Sponsoring
Unit:
GPMFC
Chair: Zheng-Tian Lu, Argonne National Laboratory
Abstract ID: BAPS.2015.DAMOP.G2.3
Abstract: G2.00003 : Single atom tagging and the quest for Majorana Neutrinos*
9:00 AM–9:30 AM
Preview Abstract
Abstract
Author:
Giorgio Gratta
(Physics Dept, Stanford University)
Elementary spin 1/2 particles (fermions) are generally described by
a 4-component Dirac wavefunction. However Nature only needs to work this way
for charged particles, where particles and antiparticles are distinguished
by the charge state. A simpler 2-component Majorana wavefunction can be used
to describe \textit{neutral} spin 1/2 particles, in which case the
particle-antiparticle and spin symmetries are related to each other. And
indeed, Majorana particles have recently emerged in the condensed matter of
topological materials. Within the Standard Model of elementary particle
physics the neutrino is the only possible candidate for a Majorana particle.
Dirac and Majorana behavior is only discernable for particles of finite
mass, since in the massless case two of the Dirac states are impossible to
reach. The recent discovery of finite neutrino masses has opened the
question of whether neutrinos are elementary Majorana particles. In the
affirmative case a new nuclear decay, the neutrinoless double-beta decay, is
possible, albeit with a half-life that becomes infinite as the mass goes to
zero. Present searches for neutrinoless double-beta decay have given
negative results, with 90{\%} CL half-lives in excess of 10$^{25}$yrs.
The next generation of experiments will use tons of a specific isotope and
search for a few nuclear decays in years of data. The challenge is, of
course, to distinguish such decays from the unavoidable background due to
trace amounts of natural radioactivity. In the nEXO project we will use tons
of the isotope $^{136}$Xe , liquefied, in a Time Projection Chamber. In
addition to more conventional (and essential) methods to suppress
backgrounds, the nEXO collaboration is developing several techniques to
recover and spectroscopically identify single atoms of the decay daughter,
$^{136}$Ba, of the double-beta decay of $^{136}$Xe. These techniques can
take advantage of ultrasensitive detection methods of atomic physics for a
second phase of the nEXO program, with goals of improving the sensitivity to
half-lives above 10$^{28}$yrs, corresponding to neutrino masses well below
10meV. I will describe the general status of the field and the R{\&}D in
progress to detect a few atoms of Ba produced in a year in tons of Xe.
*On behalf of the nEXO collaboration
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DAMOP.G2.3