  We present a new mechanism for generating the baryon asymmetry of the
universe directly in the decay of a singlet scalar field $S_r$ with a weak
scale mass and a high dimensional baryon number violating coupling. Unlike most
currently popular models, this mechanism, which becomes effective after the
electroweak phase transition, does not rely on the sphalerons for inducing a
nonzero baryon number. CP asymmetry in $S_r$ decay arises through loop diagrams
involving the exchange of $W^\pm$ gauge bosons, and is suppressed by light
quark masses, leading naturally to a value of $\eta_B \sim 10^{-10}$. We show
that the simplest realization of this mechanism, which uses a six quark $\Delta
B=2$ operator, predicts colored scalars accessible to the LHC, and
neutron--antineutron oscillation within reach of the next generation
experiments.
