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arXiv · hep-ph/0509278

Constraining invisible neutrino decays with the cosmic microwave background

Steen Hannestad·Georg Raffelt
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Abstract

Precision measurements of the acoustic peaks of the cosmic microwave background indicate that neutrinos must be freely streaming at the photon decoupling epoch when T ~ 0.3 eV. This requirement implies restrictive limits on ``secret neutrino interactions,'' notably on neutrino Yukawa couplings with hypothetical low-mass (pseudo)scalars ϕ. For diagonal couplings in the neutrino mass basis we find g < 1 x 10^-7, comparable to limits from supernova 1987A. For the off-diagonal couplings and assuming hierarchical neutrino masses we find g < 1 x 10^-11 (0.05 eV/m)^2 where m is the heavier mass of a given neutrino pair connected by g. This stringent limit excludes that the flavor content of high-energy neutrinos from cosmic-ray sources is modified by ν-> ν' + ϕdecays on their way to Earth.

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Steen Hannestad, Georg Raffelt. 2005-09-26. Constraining invisible neutrino decays with the cosmic microwave background. https://doi.org/10.1103/physrevd.72.103514

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