  We extend the standard model with two iso-singlet color triplet scalars, one
singlet real scalar and one singlet fermion. The new fields are odd under an
unbroken Z_2 discrete symmetry while the standard model particles are even. The
decays of the singlet real scalar into three standard model quarks (antiquarks)
with three singlet antifermions (fermions), which explicitly violate the baryon
number, will become effective after the electroweak phase transition and then
produce the observed baryon asymmetry in the universe through the loop diagram
involving the exchange of the W gauge boson. The singlet fermion can serve as
the candidate for cold dark matter. In our model, all new particles with masses
below the TeV scale can be detected by the forthcoming collider experiments or
the next generation experiments for neutron-antineutron oscillations.
