Differentiating Dilatons from Axions by their mixing with photons

TL;DR

This paper analyzes how dilatons and axions, scalar and pseudoscalar fields, interact differently with photons in magnetized media, proposing a method to distinguish them through their unique electromagnetic signatures.

Contribution

It investigates the distinct mixing patterns of dilatons and axions with photons in external magnetic fields, highlighting a structural difference useful for experimental identification.

Findings

Only one of the fields interacts with the longitudinal photon mode.

The mixing patterns of dilatons and axions differ structurally.

Electromagnetic signals from their mixing can be distinguished experimentally.

Abstract

According to the model ($\Lambda$CDM), based on deep cosmological observations, the current universe is constituted of 5$\%$ baryonic matter and 25 $\%$ non-baryonic cold dark matter (of speculative origin). These include quanta of scalar filed like dilaton($\phi$) of scale symmetry origin and quanta of pseudoscalar field of extra standard model symmetry ( Peccei-Quinn) origin, like axion ($\phi'$). These fields couple to di-photons through dim-5 operators. In magnetized medium, they in principle can interact with the three degrees of freedom (two transverse ($A_{\parallel,\perp}$) and one longitudinal ($A_{L}$)) of photon($\gamma$) as long as the total spin is conserved. Because of intrinsic spin being zero, both $\phi$ and $\phi'$ could in principle have interacted with $A_{L}$, (having $s_{z}=0$). However, out of $\phi$ and $\phi'$ only one interacts with $A_{L}$. Furthermore, the ambient external magnetic field and media, breaks the intrinsic Lorentz symmetry of the system invoking Charge conjugation, Parity and Time reversal symmetries, we analyse the mixing dynamics of $\phi\gamma$ and $\phi'\gamma$ systems and the structural {\it difference} of their mixing pattern. The strength of electromagnetic (EM) signals due to $\phi\gamma$ and $\phi'\gamma$ mixing as a result would be {\it different}. We conclude by commenting on the possibility of detecting this {\it difference} -- in polarimetric observables the EMS -- using the existing space-borne detectors.