Gravitational Bremsstrahlung in Collisions of Ultrarelativistic Charges in the Five-Dimensional ADD Model

Within the five-dimensional ADD model of space-time with compactification radius R, we consider the classical gravitational bremsstrahlung arising from the collision of two ultra-relativistic charges. The collision is governed by the impact parameter b and the Lorentz factor γ. Using the perturbation theory, the total energy, radiated as a gravitational wave, is calculated in the leading order in γ, as well as the spectral-angular and polarization characteristics. The radiation is characterized by concentration within a cone of opening angle of order 1/γ, with the dominant contribution coming from frequencies of order γ2/b. The average number of Kaluza-Klein emission modes is estimated to be of the order of γR/b.