  The particle production through the scalaron decays are considered for
several different channels. The central part of the work is dedicated to a
study of the decay probability into two complex minimally coupled massless
scalars. The calculations are performed by two different independent methods.
In addition we calculated the decay probability into real minimally coupled
massless scalars, conformally coupled massive scalars, massive fermions, and
gauge bosons. The results are compared with the published papers which in some
cases disagree with each other.
