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arXiv · 1412.6875

Effect of neutrino rest mass on ionization equilibrium freeze-out

E. Grohs·G. M. Fuller·C. T. Kishimoto·M. W. Paris
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Abstract

We discuss how small neutrino rest masses can increase the expansion rate near the photon decoupling epoch in the early universe, causing an earlier, higher temperature freeze-out for ionization equilibrium compared to the massless neutrino case. This yields a larger free-electron fraction. A larger ratio of the sound horizon to the photon diffusion length follows, implying a smaller inferred Neff. This neutrino-mass/recombination effect depends strongly on the neutrino rest masses. Though below current sensitivity, this effect could be probed by next-generation cosmic microwave background experiments, giving an observational handle of neutrino mass physics.

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E. Grohs, G. M. Fuller, C. T. Kishimoto, M. W. Paris. 2014-12-22. Effect of neutrino rest mass on ionization equilibrium freeze-out. https://doi.org/10.1103/physrevd.92.125027

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