Cosmological Constraints on Invisible Neutrino Decays Revisited. (arXiv:1907.05425v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Escudero_M/0/1/0/all/0/1">Miguel Escudero</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Fairbairn_M/0/1/0/all/0/1">Malcolm Fairbairn</a>
Neutrinos could decay. Invisible neutrino decay modes are difficult to target
at laboratory experiments, and current bounds on such decays from solar
neutrino and neutrino oscillation experiments are somewhat weak. It has been
known for some time that Cosmology can serve as a powerful probe of invisible
neutrino decays. In this work, we show that in order for Big Bang
Nucleosynthesis to be successful, the invisible neutrino decay lifetime should
be $tau_nu > 10^{-3},text{s}$. We revisit Cosmic Microwave Background
constraints on invisible neutrino decays, and by using the latest Planck
observations we find that neutrino lifetimes $tau_nu < (1.2-0.3)times
10^{9},text{s} , left({m_nu}/{ 0.05,text{eV} }right)^3$ are excluded at
$95%$ CL. We show that this bound is robust to modifications of the
cosmological model, in particular that it is independent of the presence of
dark radiation. We find that typical invisible neutrino decay modes with rates
$tau_nu < 10^{5},text{s}, left({m_nu}/{ 0.05,text{eV} }right)^3$ are
disfavoured at more than $5,sigma$ with respect to $Lambda$CDM given the
latest Planck CMB observations. Finally, we show that when including
high-$ell$ Planck polarization data, neutrino lifetimes $tau_nu =
(2-14)times 10^{9},text{s} , left({m_nu}/{ 0.05,text{eV} }right)^3$
are mildly preferred -- with a 1-2 $sigma$ significance -- over neutrinos
being stable.
Neutrinos could decay. Invisible neutrino decay modes are difficult to target
at laboratory experiments, and current bounds on such decays from solar
neutrino and neutrino oscillation experiments are somewhat weak. It has been
known for some time that Cosmology can serve as a powerful probe of invisible
neutrino decays. In this work, we show that in order for Big Bang
Nucleosynthesis to be successful, the invisible neutrino decay lifetime should
be $tau_nu > 10^{-3},text{s}$. We revisit Cosmic Microwave Background
constraints on invisible neutrino decays, and by using the latest Planck
observations we find that neutrino lifetimes $tau_nu < (1.2-0.3)times
10^{9},text{s} , left({m_nu}/{ 0.05,text{eV} }right)^3$ are excluded at
$95%$ CL. We show that this bound is robust to modifications of the
cosmological model, in particular that it is independent of the presence of
dark radiation. We find that typical invisible neutrino decay modes with rates
$tau_nu < 10^{5},text{s}, left({m_nu}/{ 0.05,text{eV} }right)^3$ are
disfavoured at more than $5,sigma$ with respect to $Lambda$CDM given the
latest Planck CMB observations. Finally, we show that when including
high-$ell$ Planck polarization data, neutrino lifetimes $tau_nu =
(2-14)times 10^{9},text{s} , left({m_nu}/{ 0.05,text{eV} }right)^3$
are mildly preferred — with a 1-2 $sigma$ significance — over neutrinos
being stable.
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