Study Uses CMB Spectral Distortions to Constrain Dark Photon Models
Researchers have extended the study of cosmic microwave background (CMB) spectral distortions to their anisotropic components in order to constrain models of dark photons, hypothetical gauge bosons of a dark sector. The work uses the newly developed Frequency Hierarchy framework within CosmoTherm to compute photon transfer functions and distortion cross power spectra across the dark photon parameter space. The results place complementary limits on the minimal dark photon model using Planck data, with constraints only marginally weaker than those from COBE/FIRAS monopole distortion measurements.
Dark photons are hypothetical gauge bosons associated with a dark sector and represent one of the most studied minimal extensions of the Standard Model. This preprint, submitted to the Journal of Cosmology and Astroparticle Physics, investigates scenarios in which an initially empty dark photon sector is populated through resonant photon-to-dark-photon conversions, a process that imprints observable spectral distortions on the CMB. The authors extend prior work on the monopole (average) distortion spectrum to anisotropic spectral distortions using the Frequency Hierarchy framework of CosmoTherm. Their analysis finds that the dark photon mass governs the shape and multipole-dependence of the signal power spectra, while the kinetic mixing parameter controls the overall amplitude. Applying these results to Planck data, the team derives constraints on the minimal dark photon model that are only marginally weaker than those from COBE/FIRAS monopole measurements, demonstrating the complementary power of anisotropic distortions. The study also identifies that conversions occurring at redshifts above approximately two million may introduce isocurvature-type perturbations, potentially opening new avenues for constraining the model in regimes where distortion anisotropies thermalize.
What's missing
As a preprint not yet peer-reviewed, the results have not undergone formal scientific scrutiny. The study does not fully explore non-minimal dark photon models or the impact of alternative cosmological assumptions on the derived constraints.
What different sources said
- arXiv astro-phCenter
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