Polarization Effects in γP Gravitational Scattering with Applications to Dark Matter

Using a simple perturbative approach to quantum gravity, we consider gravitational scattering
of high-energy, polarized photons on a massive scalar target. We find that due to the exchange of
virtual gravitons, there is a non-trivial polarization dependence in the photon scattering behavior,
not previously considered in the literature. Our results are considered in analogy with scattering
in quantum electrodynamics. We find that the polarization dependence in a gravitational field is
extremely weak relative to electromagnetic effects. A variety of possible experimental parameters
were considered in order to isolate the quantum gravity effects.
Using Monte-Carlo methods, this work models the gravitational scattering of galactic photons in
the Dark Matter Halo of the Milky Way. The likelihood of detecting these scattered photons on Earth
is then calculated, along with the degree of gravity-induced polarization. Detection of this polarization
would provide convincing evidence of the quantum effects of gravity and indirect proof of graviton
exchange. Our results indicate that Dark Matter can be thought as polarizing, even in scalar models
where Dark Matter only interacts gravitationally. Results also suggest a new method of bounding
the mass of the Dark Matter particle from above. Dark Matter was chosen as the scattering target to
mitigate interfering non-gravitational effects.
We also briefly discuss polarization effects of photon-scalar scattering as an entanglement breaking
channel for maximally entangled photons produced by pair annihilation, which is a fascinating avenue
for future research.