Volume 318 - Corfu Summer Institute 2017 "Schools and Workshops on Elementary Particle Physics and Gravity" (CORFU2017) - Workshop on the Standard Model and Beyond
Resonant atom Majorana mixing
J. Bernabeu* and A. Segarra
Full text: pdf
Pre-published on: August 22, 2018
Published on: August 24, 2018
Abstract
Massive neutrinos demand to ask whether they are Dirac or Majorana particles. Majorana neutri-
nos are an irrefutable proof of physics beyond the Standard Model. Neutrinoless double electron
capture is not a process but a virtual ∆L = 2 mixing between a parent $^{A}Z$ atom and a daughter
$^{A}(Z − 2)$ excited atom with two electron holes. As a mixing between two neutral atoms and the
observable signal in terms of emitted two-hole X-rays, the strategy, experimental signature and
background are different from neutrinoless double beta decay. The mixing is resonantly enhanced
for almost degeneracy and, under these conditions, there is no irreducible background from the
standard two-neutrino channel. We reconstruct the natural time history of a nominally stable par-
ent atom since its production either by nature or in the laboratory. After the time periods of atom
oscillations and the decay of the short-lived daughter atom, at observable times the relevant “sta-
tionary" states are the mixed metastable long-lived state and the short-lived excited state, as well
as the ground state of the daughter atom. Their natural population inversion is most appropriate
for exploiting the bosonic nature of the observed X-rays by means of stimulating X-ray beams.
Among different observables of the atom Majorana mixing, we include the enhanced rate of stim-
ulated X-ray emission from the long-lived metastable state by a high-intensity X-ray beam. a
gain factor of 100 can be envisaged at current XFEL facilities. On the other hand, the historical
population of the daughter atom ground state can be probed by exciting it with a current pulsed
optical laser, showing the characteristic absorption lines: the whole population can be excited in
a shorter time than typical pulse duration.
DOI: https://doi.org/10.22323/1.318.0063
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