  Recent studies reveal that the free eccentricities of Kepler-34b and
Kepler-413b are much larger than their forced eccentricities, implying that the
scattering events may take place in their formation. The observed orbital
configuration of Kepler-34b cannot be well reproduced in disk-driven migration
models, whereas a two-planet scattering scenario can play a significant role of
shaping the planetary configuration. These studies indicate that circumbinary
planets discovered by Kepler may have experienced scattering process. In this
work, we extensively investigate the scattering outcomes of circumbinary
planets focusing on the effects of planet mass ratio. We find that the
planetary mass ratio and the the initial relative locations of planets act as
two important parameters which affect the eccentricity distribution of the
surviving planets. As an application of our model, we discuss the observed
orbital configurations of Kepler-34b and Kepler-413b. We first adopt the
results from the disk-driven models as the initial conditions, then simulate
the scattering process occurred in the late evolution stage of circumbinary
planets. We show that the present orbital configurations of Kepler-34b and
Kepler-413b can be well reproduced when considering two unequal-mass planet
ejection model. Our work further suggests that some of the currently discovered
circumbinary single-planet systems may be the survivals of original
multiple-planet systems. The disk-driven migration and the scattering events
occurring in the late stage both play an irreplaceable role in sculpting the
final systems.
