KATRIN bound on 3+1 active-sterile neutrino mixing and the reactor antineutrino anomaly
C. Giunti, Yufeng Li, Y. Y. Zhang
Abstract
A bstract We present the bounds on 3+1 active-sterile neutrino mixing obtained from the first results of the KATRIN experiment. We show that the KATRIN data extend the Mainz and Troitsk bound to smaller values of $$ \Delta {m}_{41}^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>m</mml:mi> <mml:mn>41</mml:mn> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> for large mixing and improves the exclusion of the large- $$ \Delta {m}_{41}^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>m</mml:mi> <mml:mn>41</mml:mn> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> solution of the Huber-Muller reactor antineutrino anomaly. We also show that the combined bound of the Mainz, Troitsk, and KATRIN tritium experiments and the Bugey-3, NEOS, PROSPECT, and DANSS reactor spectral ratio measurements exclude most of the region in the (sin 2 2 ϑ ee , $$ \Delta {m}_{41}^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>m</mml:mi> <mml:mn>41</mml:mn> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> ) plane allowed by the Huber-Muller reactor antineutrino anomaly. Considering two new calculations of the reactor antineutrino fluxes, we show that one, that predicts a lower 235 U antineutrino flux, is in agreement with the tritium and reactor spectral ratio measurements, whereas the other leads to a larger tension than the Huber-Muller prediction. We also show that the combined reactor spectral ratio and tritium measurements disfavor the Neutrino-4 indication of large active-sterile mixing. We finally discuss the constraints on the gallium neutrino anomaly.