Bound on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math> Active-Sterile Neutrino Mixing from the First Four-Week Science Run of KATRIN

We report on the light sterile neutrino search from first four-week science run of KATRIN experiment in 2019. Beta-decay electrons a high-purity gaseous molecular tritium source are analyzed by high-resolution MAC-E filter down to 40 eV below endpoint at 18.57 keV. consider framework with three active neutrinos and one neutrino. The analysis is sensitive mass, m4, fourth mass state for m42?1000 eV2 active-to-sterile mixing |Ue4|2?2×10?2. No significant spectral distortion observed exclusion bounds reported. These new limits supersede Mainz results improve Troitsk bound m42<30 eV2. reactor gallium anomalies constrained 100<?m412<1000 eV2.Received 13 November 2020Revised 6 January 2021Accepted 22 2021DOI:https://doi.org/10.1103/PhysRevLett.126.091803Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article’s title, journal citation, DOI. Funded SCOAP3.Published SocietyPhysics Subject Headings (PhySH)Physical SystemsSterile neutrinosParticles & FieldsNuclear Physics