  We propose a low energy effective field theory of QCD at the scale of pion
mass for the $N_B=2$ sector, $N_B$ being the baryon number, which contains two
dibaryon fields in addition to the nucleons and pions. It has a well defined
counting, is renormalizable and the nucleon-nucleon scattering amplitudes are
manifestly unitary at leading order. We work out a lower energy effective
theory for nucleons with energy much lower than the pion mass and three
momentum comparable to it, which also has a well defined counting and is
renormalizable. The dibaryon fields must also be kept as explicit degrees of
freedom in this theory. We calculate the scattering amplitudes at
next-to-leading order for the $^1S_0$ and $^3S_1$ channels in this framework
and obtain an excellent description of the phase shifts for center of mass
energies in the $0-50 MeV$ range.
