New Constraints on a Light Spinless Particle Coupled to Photons

TL;DR

This work constrains a light spinless φ that couples to photons at low energies by exploiting cosmological data: the extragalactic photon background, CMB spectral distortions (Sunyaev-Zeldovich y and photon chemical potential μ), and primordial deuterium abundances. By modeling φ production and decay with τ = \frac{64\pi}{g^2 m^3} and a relic abundance $\frac{n_\phi}{n_\gamma} = 1/g_*(T_F)$ under a high-temperature desert, the authors derive new exclusions in the $(m,g)$ parameter space that strengthen prior bounds. The results show φ is unlikely to be a dark-matter component in significant regions and demonstrate cosmological observations as powerful probes of photon-coupled light bosons. The approach complements laboratory and astrophysical bounds, providing tighter constraints on photon-only couplings of light bosons relevant to extensions of the Standard Model.

Abstract

We obtain new stringent constraints on a light spinless particle phi coupled only to photons at low energies, considering its effects on the extragalactic photon background, the blackbody spectrum of the CMBR and the cosmological abundance of deuterium.