Implications of 3+1 Short-Baseline Neutrino Oscillations

TL;DR

The paper addresses short-baseline neutrino oscillations in a hierarchical 3+1 framework, incorporating KARMEN and LSND ν_e−12C scattering data to refine the global fit. It links oscillation parameters to direct mass observables via $m_{β}^{(4)} = |U_{e4}| \,\\sqrt{Δm^2_{41}}$ and $m_{ββ}^{(4)} = |U_{e4}|^2 \,\\sqrt{Δm^2_{41}}$, finding best-fit $Δm^2_{41}$ values around the sub–few eV^2 scale (0.9–1.6 eV^2) with $|U_{e4}|^2$ of a few percent, and overlapping allowed regions for appearance and disappearance data. The predicted heavy-state contributions are $m_β$ in the ~0.1–0.7 eV range and $m_{ββ}$ in the ~0.01–0.1 eV range, implying that upcoming β-decay and neutrinoless double-β decay experiments can test these scenarios. The results align with cosmological constraints on total neutrino masses, and they emphasize the potential for KATRIN and future 0νββ searches to probe or constrain a light sterile neutrino in the 1 eV range.

Abstract

We present an upgrade of the 3+1 global fit of short-baseline neutrino oscillation data obtained with the addition of KARMEN and LSND nu_e-Carbon scattering data. We discuss the implications for the measurements of the effective neutrino mass in beta-decay and neutrinoless double-beta-decay experiments. We find respective predicted ranges of about 0.1-0.7 eV and 0.01-0.1 eV.

Figures (9)

• Figure 1: Superposition of the 95% C.L. contours in the $\sin^{2}2\vartheta_{ee}$--$\Delta{m}^{2}_{41}$ plane obtained from the separate fits of Gallium, reactor and $\nu_{e}-{}^{12}\text{C}$ data and that obtained from the combined fit. The best-fit points are indicated by crosses (see Table. \ref{['tab-bef']}).
• Figure 2: KARMEN and LSND $\nu_{e}-{}^{12}\text{C}$ cross section data (points and asterisks, respectively) with the corresponding statistical error bars. The solid blue line shows the best-fit dependence of the cross section on the neutrino energy $E$ in the case of no oscillations. The dashed red and long-dashed green histograms show, respectively, the corresponding average cross section for the energy bins of the KARMEN and LSND data. The dash-dotted red and long-dash-dotted green histograms show, respectively, the average cross section modulated by the best-fit oscillation probability for the energy bins of the KARMEN and LSND data.
• Figure 3: Allowed regions in the $\sin^{2}2\vartheta_{e\mu}$--$\Delta{m}^2_{41}$, $\sin^{2}2\vartheta_{ee}$--$\Delta{m}^2_{41}$ and $\sin^{2}2\vartheta_{\mu\mu}$--$\Delta{m}^2_{41}$ planes obtained from the GLO-LOW and GLO-HIG global analyses of short-baseline neutrino oscillation data (see Tab \ref{['tab-bef']}). The best-fit points are indicated by crosses (see Table. \ref{['tab-bef']}). The thick solid blue lines with the label APP show the $3\sigma$ allowed regions obtained from the analysis of $\hbox{$\overset{(-)}{\space}$}{{\nu}_{\mu}}\to\hbox{$\overset{(-)}{\space}$}{{\nu}_{e}}$ appearance data. The thick solid red lines with the label DIS show the $3\sigma$ allowed regions obtained from the analysis of disappearance data.
• Figure 4: Marginal $\Delta\chi^2 = \chi^2 - \chi^2_{\text{min}}$ as a function of the contribution $m_{\beta}^{(4)} = |U_{e4}| \sqrt{\Delta{m}^2_{41}}$ to the effective $\beta$-decay electron-neutrino mass $m_{\beta}$ obtained from the fits of Tritium (TRI) data with Reactor (REA), Gallium (GAL) and $\nu_{e}$-${}^{12}\text{C}$ (CAR) data, their combined fit (RGCT) and the GLO-LOW and GLO-HIG global fits.
• Figure 5: Bands of the relative deviation of the Kurie plot in $\beta$-decay corresponding to the allowed regions in the $\sin^{2}2\vartheta_{ee}$--$\Delta{m}^2_{41}$ plane in Fig. \ref{['con-glo']}, obtained from the GLO-LOW global analysis of short-baseline neutrino oscillation data (see Tab \ref{['tab-bef']}). The black solid line corresponds to the best-fit point ($m_{4} = 0.94 \, \text{eV}$ and $|U_{e4}|^2 = 0.027$). The dashed, dotted and dash-dotted lines correspond, respectively, to the local minima at ($m_{4} = 1.11 \, \text{eV}$, $|U_{e4}|^2 = 0.03$), ($m_{4} = 1.27 \, \text{eV}$, $|U_{e4}|^2 = 0.035$) and ($m_{4} = 2.40 \, \text{eV}$, $|U_{e4}|^2 = 0.033$).