Differentiating Dilatons from Axions by their mixing with photons

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.