DOI 10.1007/s100520000397
The singular seesaw mechanism
with hierarchical Dirac neutrino mass
Y. Chikira1 - N. Haba2 - Y. Mimura3
1 Department of Physics, Tokyo Institute of Technology Oh-okayama, Meguro, Tokyo 152-0033, Japan
2 Faculty of Engineering, Mie University, Mie, 514-0008, Japan
3 Theory Group, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801, Japan
Received: 14 July 1999 / Revised version: 14 March 2000 /
Published online: 26 July 2000 - © Springer-Verlag 2000
Abstract
The singular seesaw mechanism can naturally explain
the atmospheric neutrino deficit
by maximal oscillations between
and
.
This mechanism can also induce
three different scales
of the neutrino mass squared differences,
which can explain the neutrino deficits of
three independent experiments
(solar, atmospheric, and LSND) by
neutrino oscillations.
In this paper we show that
realistic mixing angles
among the neutrinos can be obtained
by introducing a hierarchy
in the Dirac neutrino mass.
In the case where the Majorana neutrino mass matrix
has rank 2, the solar neutrino deficit is explained
by vacuum oscillations between 
and 
.
We also consider the case where the Majorana neutrino mass
matrix has rank 1.
In this case, the matter enhanced
Mikheyev-Smirnov-Wolfenstein solar neutrino solution is
preferred as the solution of the solar neutrino deficit.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
