  In traditional models only an order one fraction of energy is transferred
from the inflaton to radiation through nonperturbative resonance production in
preheating immediately after inflation, due to backreaction effects. We propose
a particle production mechanism that could improve the depletion of the
inflaton energy density by up to four orders of magnitude. The improvement
comes from the fast perturbative decays of resonantly produced daughter
particles. They act as a "spillway" to drain these daughter particles, reducing
their backreaction on the inflaton and keeping the resonant production
effective for a longer period. Thus we dub the scenario "spillway preheating".
We also show that the fraction of energy density remaining in the inflaton has
a simple inverse power-law scaling in the scenario. In general, spillway
preheating is a much more efficient energy dissipation mechanism, which may
have other applications in model building for particle physics.
