Constraints on hidden photons from current and future observations of CMB spectral distortions

Understand

A variety of beyond the standard model scenarios contain very light hidden sector U(1) gauge bosons undergoing kinetic mixing with the photon.

• The resulting oscillation between ordinary and hidden photons leads to spectral distortions of the cosmic microwave background.
• We update the bounds on the mixing parameter $\chi_0$ and the mass of the hidden photon $m_{\gamma'}$ for future experiments measuring CMB spectral distortions, such as PIXIE and PRISM/COrE.
• For $10^{-14}\;{\rm eV}\lesssim m_{\gamma'}\lesssim 10^{-13}\;{\rm eV}$, we find the kinetic mixing angle $\chi_0$ has to be less than $10^{-8}$ at 95\% CL.