  We discuss the neutrino mass matrix based on the Occam's Razor approach in
the framework of the seesaw mechanism. We impose four zeros in the Dirac
neutrino mass matrix, which give the minimum number of parameters needed for
the observed neutrino masses and lepton mixing angles, while the charged lepton
mass matrix and the right-handed Majorana neutrino mass matrix are taken to be
real diagonal ones. The low-energy neutrino mass matrix has only seven physical
parameters. We show successful predictions for the mixing angle $\theta_{13}$
and the CP violating phase $\delta_{CP}$ with the normal mass hierarchy of
neutrinos by using the experimental data on the neutrino mass squared
differences, the mixing angles $\theta_{12}$ and $\theta_{23}$. The most
favored region of $\sin\theta_{13}$ is around $0.13\sim 0.15$, which is
completely consistent with the observed value. The CP violating phase
$\delta_{CP}$ is favored to be close to $\pm \pi/2$. We also discuss the
Majorana phases as well as the effective neutrino mass for the neutrinoless
double-beta decay $m_{ee}$, which is around $7\sim 8$ meV. It is extremely
remarkable that we can perform a "complete experiment" to determine the
low-energy neutrino mass matrix, since we have only seven physical parameters
in the neutrino mass matrix. In particular, two CP violating phases in the
neutrino mass matrix are directly given by two CP violating phases at high
energy. Thus, assuming the leptogenesis we can determine the sign of the cosmic
baryon in the universe from the low-energy experiments for the neutrino mass
matrix.
