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On the Effective Mass of the Electron Neutrino in Beta Decay

Y. Farzan·A. Yu. Smirnov
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Abstract

In the presence of mixing between massive neutrino states, the distortion of the electron spectrum in beta decay is, in general, a function of several masses and mixing angles. For $3ν$-schemes which describe the solar and atmospheric neutrino data, this distortion can be described by a single effective mass, under certain conditions. In the literature, two different definitions for the effective mass have been suggested. We show that for quasi-degenerate mass schemes (with an overall mass scale $m$ and splitting $Δm^2$) the two definitions coincide up to $(Δm^2)^2/m^4$ corrections. We consider the impact of different effective masses on the integral energy spectrum. We show that the spectrum with a single mass can be used also to fit the data in the case of $4ν$-schemes motivated, in particular, by the LSND results. In this case the accuracy of the mass determination turns out to be better than $(10 - 15)%$.

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Y. Farzan, A. Yu. Smirnov. 2003-03-17. On the Effective Mass of the Electron Neutrino in Beta Decay. https://doi.org/10.1016/s0370-2693(03)00207-7

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