Unbounded energies of debris from head-on particle collisions near black holes

TL;DR

This paper investigates how head-on collisions near black holes can produce debris with unbounded energies at infinity, overcoming redshift limitations, especially through multiple scattering processes.

Contribution

It demonstrates that head-on collisions can generate unbounded debris energy at infinity, a novel scenario involving particles moving away from the black hole after prior collisions.

Findings

Unbounded energy of debris at infinity in head-on collisions.

Multiple scattering enables particles to escape with high energy.

Redshift does not limit debris energy in this scenario.

Abstract

If two particles move toward a black hole and collide near the horizon, the energy E_{c.m.} in the centre of mass can grow unbounded. This is a so-called Ba\~nados-Silk-West (BSW) effect. One of problems creating obstacles to the possibility of its observation consists in that individual energy E of a fragment at infinity remains finite because of redshift. We show that in the case of head-on collision, debris may have unbounded energy E. An essential ingredient of this scenario is a particle moving away from a black hole in the near-horizon region. It can appear due to precedent collision that implies multiple scattering.