Aspects of Planckian Scattering beyond the Eikonal

TL;DR

This paper explores the computation of two-particle scattering amplitudes at Planckian energies beyond the eikonal approximation, revealing new pole structures and complex interactions between electromagnetic and gravitational effects at higher orders.

Contribution

It introduces a method to analyze scattering amplitudes beyond the eikonal limit, highlighting novel pole structures and the interplay of electromagnetic and gravitational effects at higher momentum transfers.

Findings

Amplitude poles differ from eikonal limit for neutral particles

Electromagnetic and gravitational effects decouple at leading order

Higher-order corrections show non-trivial mixing of effects

Abstract

We discuss an approach to compute two-particle scattering amplitudes for spinless particles colliding at Planckian centre-of-mass energies, with increasing momentum transfer away from the eikonal limit. For electrically neutral particles, the amplitude exhibits poles on the imaginary squared cm energy axis at locations that are distinct from those appearing in the eikonal limit. For charged particles, electromagnetic and gravitational effects remain decoupled for the eikonal situation as also the leading order (in momentum transfer, or equivalently, the impact parameter) correction, but mix non-trivially for higher orders.