Update of Short-Baseline Electron Neutrino and Antineutrino Disappearance

TL;DR

The paper updates electron-neutrino and electron-antineutrino disappearance analyses within a 3+1 sterile-neutrino framework, incorporating the Gallium anomaly, the reactor anomaly, solar data, and ν_e–C scattering with updated cross sections. A global χ^2 analysis across these data sets, plus Mainz β-decay and EXO neutrinoless double-beta decay constraints, maps allowed regions in the ($\Delta m^2_{41}$, $\sin^2 2\vartheta_{ee}$) plane and reveals a compatible short-baseline signal with $Δm^2_{41}$ in the eV^2 range and moderate mixing. The results indicate a best-fit near $\Delta m^2_{41} \approx 7.6\,\text{eV}^2$ and $\sin^2 2\vartheta_{ee} \approx 0.12$, with a secondary 1σ region around $Δm^2_{41} \approx 2\,\text{eV}^2$ and $\sin^2 2\vartheta_{ee} \approx 0.1$, while external constraints disfavor very large $Δm^2_{41}$. These findings motivate upcoming very-short-baseline ν_e experiments and illustrate how laboratory β-decay, 0νββ searches, and cosmology provide complementary protections of the sterile-neutrino parameter space.

Abstract

We present a complete update of the analysis of electron neutrino and antineutrino disappearance experiments in terms of neutrino oscillations in the framework of 3+1 neutrino mixing, taking into account the Gallium anomaly, the reactor anomaly, solar neutrino data and nu_e-C scattering data. We discuss the implications of a recent 71Ga(3He,3H)71Ge measurement which give information on the neutrino cross section in Gallium experiments. We discuss the solar bound on active-sterile mixing and present our numerical results. We discuss the connection between the results of the fit of neutrino oscillation data and the heavy neutrino mass effects in beta-decay experiments (considering new Mainz data) and neutrinoless double-beta decay experiments (considering the recent EXO results).

Figures (18)

• Figure 1: ${}^{71}\text{Ga}\to{}^{71}\text{Ge}$ transitions induced by ${}^{51}\text{Cr}$ and ${}^{37}\text{Ar}$ electron neutrinos.
• Figure 2: Allowed regions in the $\sin^{2}2\vartheta_{ee}$--$\Delta{m}^{2}_{41}$ plane and marginal $\Delta\chi^{2}$'s for $\sin^{2}2\vartheta_{ee}$ and $\Delta{m}^{2}_{41}$ obtained from the combined fit of the results of the Gallium radioactive source experiments in the HK case (see the text). The best-fit point corresponding to $\chi^2_{\text{min}}$ is indicated by a cross.
• Figure 3: Allowed regions and marginal $\Delta\chi^{2}$'s analogous to those in Fig. \ref{['fig:fit-ghk']} for the FF case.
• Figure 4: Allowed regions and marginal $\Delta\chi^{2}$'s analogous to those in Fig. \ref{['fig:fit-ghk']} for the HF case.
• Figure 5: Ratio $R$ of the observed $\bar{\nu}_{e}$ event rate and that expected in absence of $\bar{\nu}_{e}$ disappearance in reactor neutrino experiments. The horizontal band represents the average value of $R$ with $1\sigma$ uncertainties.