Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, $\mathrm{MINOS}+$, Daya Bay, and Bugey-3 Experiments

Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and $\mathrm{MINOS}+$ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the ${\theta }_{\mu e}$ mixing angle are derived that constitute the most constraining limits to date over five orders of magnitude in the mass-squared splitting $\mathrm{\Delta }{m}_{41}^2$, excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% ${\mathrm{CL}}_s$ for $\mathrm{\Delta }{m}_{41}^2<13{\mathrm{eV}}^2$. Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% ${\mathrm{CL}}_s$ for $\mathrm{\Delta }{m}_{41}^2<1.6{\mathrm{eV}}^2$.

Figure 1

The Feldman-Cousins (FC) exclusion region at 90% C.L. from the analysis of 1230 days of Daya Bay data is shown as the solid blue line. The 90% C.L. median sensitivity is shown as the dashed red line, along with $1\sigma$ and $2\sigma$ bands. The excluded region for the original Bugey-3 limit with the raster scan technique is shown in green, while the resulting ${\mathrm{CL}}_s$ contour from Daya Bay and its combination with the reproduced Bugey-3 results with adjusted fluxes are shown in grey and black, respectively. The regions to the right of the curves are excluded at the 90% ${\mathrm{CL}}_s$ or 90% C.L.

Figure 2

Comparison of the MINOS and $\mathrm{MINOS}+$ 90% C.L. exclusion contour using the Feldman-Cousins method [53] and the ${\mathrm{CL}}_s$ method. The regions to the right of the curves are excluded at the 90% C.L. (${\mathrm{CL}}_s$). The 90% C.L. median sensitivity is shown in red along with the $1\sigma$ and $2\sigma$ bands.

Figure 3

Comparison of the MINOS, $\mathrm{MINOS}+$, Daya Bay, and Bugey-3 combined 90% ${\mathrm{CL}}_s$ limit on ${\sin }^{2}2{\theta }_{\mu e}$ to the LSND and MiniBooNE 90% C.L. allowed regions. Regions of parameter space to the right of the red contour are excluded. The regions excluded at 90% C.L. by the KARMEN2 Collaboration [55] and the NOMAD Collaboration [56] are also shown. The combined limit also excludes the 90% C.L. region allowed by a fit to global data by Gariazzo et al. where MINOS, $\mathrm{MINOS}+$, Daya Bay, and Bugey-3 are not included [57, 58], and the 90% C.L. region allowed by a fit to all available appearance data by Dentler et al. [59] updated with the 2018 MiniBooNE appearance results [21].

Figure 4

Comparison of the MINOS, $\mathrm{MINOS}+$, Daya Bay, and Bugey-3 combined 99% ${\mathrm{CL}}_s$ limit on ${\sin }^{2}2{\theta }_{\mu e}$ to the LSND and MiniBooNE 99% C.L. allowed regions. The limit also excludes the 99% C.L. region allowed by a fit to global data by Gariazzo et al. where MINOS, $\mathrm{MINOS}+$, Daya Bay, and Bugey-3 are not included [57, 58], and the 99% C.L. region allowed by a fit to all available appearance data by Dentler et al. [59] updated with the 2018 MiniBooNE appearance results [21].