Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?

TL;DR

This paper investigates how mixing effects can suppress signals of nearly degenerate resonances in Split-UED models at the LHC, potentially causing some new physics signatures to be missed.

Contribution

It demonstrates that width mixing effects do not significantly alter the production cross sections of level-2 KK gauge bosons in Split-UED due to the Standard Model's group structure.

Findings

Large cross section modifications are absent for level-2 KK gauge bosons.

Group theoretical structure of the SM explains the suppression.

Potential implications for collider searches of new physics.

Abstract

The mixing of the imaginary parts of the transition amplitudes of nearby resonances via the breakdown of the Breit-Wigner approximation has been shown to lead to potentially large modifications in the signal rates for new physics at colliders. In the case of suppression, this effect may be significant enough to lead to some new physics signatures being initially missed in searches at, e.g., the LHC. Here we explore the influence of this `width mixing' on the production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge bosons present in Split-UED. We demonstrate that in this particular case large cross section modifications in the resonance region are necessarily absent and explain why this is so based on the group theoretical structure of the SM.