Dark matter interacting via a massive spin-2 mediator in warped extra-dimensions

TL;DR

This paper investigates dark matter interactions mediated by a massive spin-2 particle in warped extra dimensions, revealing that including the full KK tower cancels unphysical growth in annihilation channels, challenging simplified EFT approaches.

Contribution

It introduces a comprehensive analysis of KK graviton towers in warped extra dimensions for dark matter interactions, highlighting the limitations of effective field theories at high energies.

Findings

Growth in annihilation channels cancels when full KK tower is included.

Simplified EFTs may not be valid at energies above the first graviton mass.

Revisits parameter space for scalar dark matter with gravitational interactions.

Abstract

We study dark matter interacting via a massive spin-2 mediator. To have a consistent effective theory for the spin-2 particle, we work in a warped extra-dimensional model such that the mediator(s) are the Kaluza-Klein (KK) modes of the 5D graviton. We pay close attention to dark matter annihilations into KK-gravitons. Due to the high energy behavior of longitudinal modes of spin-2 fields, these channels exhibit a tremendous growth at large center of mass energies $\sqrt{s}$ if only one spin-2 mediator is considered. For the first time, we include the full KK-tower in this dark matter production process and find that this growth is unphysical and cancels once the full field content of the extra-dimensional theory is taken into account. Interestingly, this implies that it is not possible to approximate the results obtained in the full theory with a reduced set of effective interactions once $\sqrt{s}$ is greater than the first graviton mass. This casts some doubt on the universal applicability of previous studies with spin-2 mediators within an EFT framework and prompts us to revisit the phenomenological allowed parameter space of gravitationally interacting scalar dark matter in warped extra-dimensions.