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Register a new userSub-eV upper limits on neutrino masses from cosmology
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Authors
Oystein Elgaroy
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Upper limits on neutrino masses from cosmology have been reported recently to reach the impressive sub-eV level, which is competitive with future terrestrial neutrino experiments. In this brief review of the latest limits from cosmology we point out some of the caveats that should be borne in mind when interpreting the significance of these limits.
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Upper limits on neutrino masses from cosmology have been reported recently to reach the impressive sub-eV level, which is competitive with future terrestrial neutrino experiments. In this brief overview of the latest limits from cosmology I point out some of the caveats that should be borne in mind when interpreting the significance of these limits.
The Heidelberg-Moscow experiment gives the most stringent limit on the Majorana neutrino mass. After 24 kg yr of data with pulse shape measurements, we set a lower limit on the half-life of the neutrinoless double beta decay in 76Ge of T_1/2 > 5.7 * 10^{25} yr at 90% C.L., thus excluding an effective Majorana neutrino mass greater than 0.2 eV. This allows to set strong constraints on degenerate neutrino mass models.
We report a search result for a light sterile neutrino oscillation with roughly 2200 live days of data in the RENO experiment. The search is performed by electron antineutrino ($overline{ u}_e$) disappearance taking place between six 2.8 GW$_{text{th}}$ reactors and two identical detectors located at 294 m (near) and 1383 m (far) from the center of reactor array. A spectral comparison between near and far detectors can explore reactor $overline{ u}_e$ oscillations to a light sterile neutrino. An observed spectral difference is found to be consistent with that of the three-flavor oscillation model. This yields limits on $sin^{2} 2theta_{14}$ in the $10^{-4} lesssim |Delta m_{41}^2| lesssim 0.5$ eV$^2$ region, free from reactor $overline{ u}_e$ flux and spectrum uncertainties. The RENO result provides the most stringent limits on sterile neutrino mixing at $|Delta m^2_{41}| lesssim 0.002$ eV$^2$ using the $overline{ u}_e$ disappearance channel.
We report the results of the second measurement campaign of the Karlsruhe Tritium Neutrino (KATRIN) experiment. KATRIN probes the effective electron anti-neutrino mass, $m_{ u}$, via a high-precision measurement of the tritium $beta$-decay spectrum close to its endpoint at $18.6,mathrm{keV}$. In the second physics run presented here, the source activity was increased by a factor of 3.8 and the background was reduced by $25,%$ with respect to the first campaign. A sensitivity on $m_{ u}$ of $0.7,mathrm{eV/c^2}$ at $90,%$ confidence level (CL) was reached. This is the first sub-eV sensitivity from a direct neutrino-mass experiment. The best fit to the spectral data yields $m_{ u}^2 = (0.26pm0.34),mathrm{eV^4/c^4}$, resulting in an upper limit of $m_{ u}<0.9,mathrm{eV/c^2}$ ($90,%$ CL). By combining this result with the first neutrino mass campaign, we find an upper limit of $m_{ u}<0.8,mathrm{eV/c^2}$ ($90,%$ CL).
Here we give a brief review on the current bounds on the general Majorana transition neutrino magnetic moments (TNMM) which cover also the conventional neutrino magnetic moments (NMM). Leptonic CP phases play a key role in constraining TNMMs. While the Borexino experiment is the most sensitive to the TNMM magnitudes, one needs complementary information from reactor and accelerator experiments in order to probe the complex CP phases.
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