  A certain quadratic gravity model provides a successfully inflationary
scenario. The inflation is driven by the new scalar degree of freedom called
scalaron. After the end of inflation the scalaron decays in matter and dark
matter degrees of freedom reheating the Universe. We study new channels by
which the scalaron can transfer energy to the matter sector. These channels are
annihilation and decay via intermediate graviton states. Results are obtained
within perturbative quantum gravity. In the heavy scalaron limit only scalar
particles are produced by the annihilation channel. Scalaron decays in all
types of particles are allowed. In the light scalaron limit decay channel is
strongly suppressed. Boson production via the annihilation channel is expected
to be dominant at the early stages of reheating, while fermion production will
dominate later stages.
