  Single right-handed neutrino dominance (SRHND) in the 23 sector of the light
effective neutrino mass matrix has been proposed as a natural explanation for
the concurrent large 23 mixing angle and large 23 mass hierarchy. In this paper
we show how large 12 mixing angles, suitable for the large mixing angle (LMA)
MSW solution to the solar neutrino problem, may arise from SRHND. In order to
understand the conditions for SRHND and LMA MSW we first consider the case of
one and two right-handed neutrinos, and obtain simple analytic conditions which
are then extended to the case of three right-handed neutrinos. We then
introduce a single U(1) family symmetry and show how these analytic conditions
may be translated into U(1) charge assignments and perform a systematic search
for the simplest examples.
