https://doi.org/10.1140/epjc/s10052-017-4777-x
Letter
The effective neutrino mass of neutrinoless double-beta decays: how possible to fall into a well
1
Institute of High Energy Physics and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
2
Department of Physics, Liaoning Normal University, Dalian, 116029, China
3
Center for High Energy Physics, Peking University, Beijing, 100080, China
* e-mail: zhaozhenhua@ihep.ac.cn
Received:
22
February
2017
Accepted:
19
March
2017
Published online:
27
March
2017
The neutrinoless double-beta (
) decay is currently the only feasible process in particle and nuclear physics to probe whether massive neutrinos are the Majorana fermions. If they are of a Majorana nature and have a normal mass ordering, the effective neutrino mass term 
of a decay may suffer significant cancellations among its three components and thus sink into a decline, resulting in a “well” in the three-dimensional graph of 
against the smallest neutrino mass 
and the relevant Majorana phase 
. We present a new and complete analytical understanding of the fine issues inside such a well, and identify a novel threshold of in terms of the neutrino masses and flavor mixing angles: 
in connection with 
and 
. This threshold point, which links the local minimum and maximum of , can be used to signify observability or sensitivity of the future -decay experiments. Given current neutrino oscillation data, the possibility of 
is found to be very small.
© The Author(s), 2017
