Collider Signals of Gravitational Fixed Points

TL;DR

This paper explores how a non-Gaussian fixed point in quantum gravity could influence collider signals, showing that it weakens gravity at high energies and improves unitarity, with observable effects in KK graviton processes at the LHC and ILC.

Contribution

It introduces a form factor modeling the running of gravitational coupling due to a fixed point and analyzes its impact on collider phenomenology and unitarity in extra-dimensional models.

Findings

Significant effects in KK graviton exchange and production at colliders.

Form factor improves perturbative unitarity at high energies.

Processes involving KK graviton emission are less sensitive to the form factor.

Abstract

Recent studies have shown that the poor perturbative behavior of General Relativity in the ultraviolet regime may be ameliorated by the existence of a non-Gaussian fixed point which renders the theory asymptotically safe and possibly non-perturbatively renormalizable. This results in a running of the (effective) gravitational coupling such that gravity becomes weaker at high energies. We parameterize this effective coupling with a form factor and study its consequences at the LHC and ILC in models with large extra dimensions or warped extra dimensions. We find significant effects in the processes of Kaluza-Klein (KK) graviton exchange or resonant KK graviton production in both the Drell-Yan reaction as well as in $e^+e^-\to f\bar f$. On the otherhand, processes leading to KK graviton emission show qualitatively less sensitivity to the presence of a form factor. In addition, we examine tree-level perturbative unitarity in $2\to 2$ gravity-mediated scattering and find that this form factor produces a far better behaved amplitude at large center of mass energies.