Split Fermions in Extra Dimensions and Exponentially Small Cross-Sections at Future Colliders

TL;DR

The paper proposes that in theories with extra dimensions, fermions localized on separate walls lead to exponentially suppressed scattering cross sections at high energies, providing a novel experimental signature for such models.

Contribution

It introduces a new experimental signature for extra-dimensional theories where fermions are separated in the bulk, resulting in exponentially small cross sections at high energies.

Findings

Cross sections vanish exponentially at high energies for separated fermions.

Future colliders can probe inverse fermion separations up to 10-70 TeV.

Separation prevents direct couplings, solving the proton decay problem.

Abstract

We point out a dramatic new experimental signature for a class of theories with extra dimensions, where quarks and leptons are localized at slightly separated parallel ``walls'' whereas gauge and Higgs fields live in the bulk of the extra dimensions. The separation forbids direct local couplings between quarks and leptons, allowing for an elegant solution to the proton decay problem. We show that scattering cross sections for collisions of fermions which are separated in the extra dimensions vanish exponentially at energies high enough to probe the separation distance. This is because the separation puts a lower bound on the attainable impact parameter in the collision. We present cross sections for two body high energy scattering and estimate the power with which future colliders can probe this scenario, finding sensitivity to inverse fermion separations of order 10-70 TeV.