Statistical Significance of the Gallium Anomaly

Abstract

We calculate the statistical significance of the anomalous deficit of electron neutrinos measured in the radioactive source experiments of the GALLEX and SAGE solar neutrino detectors taking into account the uncertainty of the detection cross section. We found that the statistical significance of the anomaly is about 3.0 sigma. A fit of the data in terms of neutrino oscillations favors at about 2.7 sigma short-baseline electron neutrino disappearance with respect to the null hypothesis of no oscillations.

Figures (2)

• Figure 1: Solid lines: probability distributions $p_{R^{\text{Ga}}_{\text{B}}}(r)$ and $p_{R^{\text{Ga}}}(r)$, as indicated by the labels. Dashed, dotted, dash-dotted and dash-dot-dotted lines: probability distributions $p_{R^{\text{G1}}_{\text{B}}}(r)$, $p_{R^{\text{G2}}_{\text{B}}}(r)$, $p_{R^{\text{S1}}_{\text{B}}}(r)$ and $p_{R^{\text{S2}}_{\text{B}}}(r)$, respectively.
• Figure 2: Allowed regions in the $\sin^{2}2\vartheta$--$\Delta{m}^{2}$ plane and marginal $\Delta\chi^{2}$'s for $\sin^{2}2\vartheta$ and $\Delta{m}^{2}$ obtained from the combined fit of the results of the two GALLEX ${}^{51}\text{Cr}$ radioactive source experiments and the SAGE ${}^{51}\text{Cr}$ and ${}^{37}\text{Ar}$ radioactive source experiments. The best-fit point corresponding to $\chi^2_{\text{min}}$ is indicated by a cross.