Ghosts in the Wall

TL;DR

This paper explores the theoretical possibility of ghost-like axion particles with unusual kinetic properties and analyzes how they could produce detectable signals in light-shining-through-wall experiments.

Contribution

It introduces the concept of ghostly ALPs arising from higher-derivative theories and calculates their potential experimental signatures.

Findings

Ghost ALPs can lead to observable effects in photon regeneration experiments.

The presence of ghost ALPs modifies the expected signals in light-shining-through-wall setups.

Theoretical framework for ghost ALPs in higher-derivative theories is developed.

Abstract

We consider the possibility of an axion-like particle (ALP) that is a ghost, with wrong-sign kinetic and mass terms. Such an ALP can arise as the partner to an ordinary particle in theories with higher-derivative quadratic terms. We compute the photon regeneration probability in light-shining-through-wall experiments and show that the presence of such a ghostly ALP can lead, in principle, to discernible effects.