Search for heavy neutral leptons using tau lepton decays at BaBaR

Abstract

This article presents a model-independent search for an additional, mostly sterile, heavy neutral lepton (HNL), that is capable of mixing with the Standard Model τ neutrino with a mixing strength of |Uτ4|2, corresponding to the absolute square of the extended Pontecorvo-Maki-Nakagawa-Sakata matrix element. Data from the BABAR experiment, with a total integrated luminosity of 424 fb−1, are analyzed using a kinematic approach that makes no assumptions on the model behind the origins of the HNL, its lifetime or decay modes. No significant signal is found. Upper limits on |Uτ4|2 at the 95% confidence level, depend on the HNL mass hypothesis and vary from 2.31×10−2 to 5.04×10−6 (with all uncertainties considered), across the mass range 100<m4<1300 MeV/c2; the more stringent limits being placed at higher masses.3 MoreReceived 21 July 2022Accepted 13 September 2022DOI:https://doi.org/10.1103/PhysRevD.107.052009Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBaryogenesis & leptogenesisExtensions of fermion sectorNeutrino interactionsNeutrino oscillationsParticle dark matterParticles & Fields