  We calculate the nucleon-nucleon scattering amplitudes in the 1S0 and 3S1-3D1
channels at next-to-next to leading order starting from a recently proposed
non-relativistic chiral effective theory, which includes dibaryon fields as
fundamental degrees of freedom. We restrict ourselves to center of mass
energies (E) smaller than the pion mass (m_pi), and further divide the
calculation into two relative momentum (p) regions, a high energy one p ~ m_pi
>> delta m_i, \delta m_i being the dibaryon residual masses, and low energy one
p ~ delta m_i. We first match to a lower energy effective theory in which we
calculate the amplitudes in the high energy region. We further match this
effective theory to the so called pionless effective theory in the low energy
region, and carry out the calculations in the latter. Dimensional
regularization and minimal subtraction scheme are used throughout. For 1S0
channel a good description of the phase shift data is obtained for E < 50 MeV.
For the 3S1-3D1 channel, the 3S1 phase shift data is only well described up to
E < 20 MeV.
