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Register a new userBounds on light sterile neutrino mass and mixing from cosmology and laboratory searches
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We provide a consistent framework to set limits on properties of light sterile neutrinos coupled to all three active neutrinos using a combination of the latest cosmological data and terrestrial measurements from oscillations, $beta$-decay and neutrinoless double-$beta$ decay ($0 ubetabeta$) experiments. We directly constrain the full $3+1$ active-sterile mixing matrix elements $|U_{alpha4}|^2$, with $alpha in ( e,mu ,tau )$, and the mass-squared splitting $Delta m^2_{41} equiv m_4^2-m_1^2$. We find that results for a $3+1$ case differ from previously studied $1+1$ scenarios where the sterile is only coupled to one of the neutrinos, which is largely explained by parameter space volume effects. Limits on the mass splitting and the mixing matrix elements are currently dominated by the cosmological data sets. The exact results are slightly prior dependent, but we reliably find all matrix elements to be constrained below $|U_{alpha4}|^2 lesssim 10^{-3}$. Short-baseline neutrino oscillation hints in favor of eV-scale sterile neutrinos are in serious tension with these bounds, irrespective of prior assumptions. We also translate the bounds from the cosmological analysis into constraints on the parameters probed by laboratory searches, such as $m_beta$ or $m_{beta beta}$, the effective mass parameters probed by $beta$-decay and $0 ubetabeta$ searches, respectively. When allowing for mixing with a light sterile neutrino, cosmology leads to upper bounds of $m_beta < 0.09$ eV and $m_{beta beta} < 0.07$ eV at 95% C.L, more stringent than the limits from current laboratory experiments.
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In this work we update the bounds on $sum m_{ u}$ from latest publicly available cosmological data and likelihoods using Bayesian analysis, while explicitly considering particular neutrino mass hierarchies. In the minimal $Lambdatextrm{CDM}+sum m_{ u}$ model with most recent CMB data from Planck 2018 TT,TE,EE, lowE, and lensing; and BAO data from BOSS DR12, MGS, and 6dFGS, we find that at 95% C.L. the bounds are: $sum m_{ u}<0.12$ eV (degenerate), $sum m_{ u}<0.15$ eV (normal), $sum m_{ u}<0.17$ eV (inverted). The bounds vary across the different mass orderings due to different priors on $sum m_{ u}$. Also, we find that the normal hierarchy is very mildly preferred relative to the inverted, using both minimum $chi^2$ values and Bayesian Evidence ratios. In this paper we also provide bounds on $sum m_{ u}$ considering different hierarchies in various extended cosmological models: $Lambdatextrm{CDM}+sum m_{ u}+r$, $wtextrm{CDM}+sum m_{ u}$, $w_0 w_a textrm{CDM}+sum m_{ u}$, $w_0 w_a textrm{CDM}+sum m_{ u}$ with $w(z)geq -1$, $Lambda textrm{CDM} + sum m_{ u} + Omega_k$, and $Lambda textrm{CDM} + sum m_{ u} + A_{textrm{Lens}}$. We do not find any strong evidence of normal hierarchy over inverted hierarchy in the extended models either.
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