The flavor of quantum gravity

TL;DR

This paper develops an effective field theory for non-thermal quantum black holes interacting with Standard Model particles, estimating their effects on low-energy observables and deriving bounds on the Planck mass.

Contribution

It introduces a novel effective Lagrangian for quantum black holes and evaluates their impact on particle physics observables, providing new bounds on the Planck scale.

Findings

Weak bounds on the Planck mass from muon and neutron measurements

Stronger bounds from proton decay, around 10^6 GeV

Chiral suppression reduces the impact on low-energy observables

Abstract

We develop an effective field theory to describe the coupling of non-thermal quantum black holes to particles such as those of the Standard Model. The effective Lagrangian is determined by imposing that the production cross section of a non-thermal quantum black hole be given by the usual geometrical cross section. Having determined the effective Lagrangian, we estimate the contribution of a virtual hole to the anomalous magnetic moment of the muon, $\mu \to e \gamma$ transition and to the electric dipole moment of the neutron. We obtain surprisingly weak bounds on the Planck mass due to a chiral suppression factor in the calculated low energy observables. The tightest bounds come from $\mu \to e \gamma$ and the limit on the neutron electric dipole moment. These bounds are in the few TeV region. However, the bound obtained from proton decay is much more severe and of the order of $1 \times 10^6$ GeV.