Search for Active-Sterile Antineutrino Mixing Using Neutral-Current Interactions with the NOvA Experiment

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This Letter reports results from the first long-baseline search for sterile antineutrinos mixing in an accelerator-based antineutrino-dominated beam. The rate of neutral-current interactions in the two NOvA detectors, at distances of 1 and 810 km from the beam source, is analyzed using an exposure of $12.51\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons-on-target from the NuMI beam at Fermilab running in antineutrino mode. A total of 121 of neutral-current candidates are observed at the far detector, compared to a prediction of $122\ifmmode\pm\else\textpm\fi{}11(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}15(\mathrm{syst}.)$ assuming mixing only between three active flavors. No evidence for ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{s}$ oscillation is observed. Interpreting this result within a $3+1$ model, constraints are placed on the mixing angles ${\ensuremath{\theta}}_{24}<25\ifmmode^\circ\else\textdegree\fi{}$ and ${\ensuremath{\theta}}_{34}<32\ifmmode^\circ\else\textdegree\fi{}$ at the 90% C.L. for $0.05\text{ }\text{ }{\mathrm{eV}}^{2}\ensuremath{\le}\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}\ensuremath{\le}0.5\text{ }\text{ }{\mathrm{eV}}^{2}$, the range of mass splittings that produces no significant oscillations at the near detector. These are the first $3+1$ confidence limits set using long-baseline accelerator antineutrinos.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.