Planckian Scatterings of Massive Particles and Gravitational Shock Waves

The scattering process of two particles at Planck energies or beyond is calculated using the gravitational shock wave metric for a massive black hole. Then, the scattering between a heavy mass particle and a small mass one is deal with. The cross section contains an extra new term of $\sigma \propto G^3$ as the correction term of the leading term derived by 't Hooft. The ultrarelativistic limit of the Lorentz boosted Reissner--Norstrom black hole is also calculated.