Neutrino dipole portal at electron colliders

We propose to search for a heavy neutral lepton (HNL), that is also known as sterile neutrino, in electron colliders running with the center-of-mass energies at few GeV, including BESIII, Belle II, and the proposed Super Tau Charm Factory (STCF). We consider the HNL interacting with Standard Model neutrino and photon via a transition magnetic moment, the so-called dipole portal. We use the monophoton signature at electron colliders to probe the constraints on the active-sterile neutrino transition magnetic moments d as the function of the HNL's mass m(N). It is found that BESIII, Belle II and STCF can probe the upper limits for d down to 1.3 x 10(-5) GeV-1, 8 x 10(-6) GeV-1, and 1.3 x 10(-6) GeV-1 with mN around GeV scale, respectively, and have sensitivity to the previously unexplored parameter space for electron-(d(e)) and tau-neutrino (d(tau)) dipole portal with m(N) from dozens to thousands MeV. On d(mu) for HNL mixing with the muon-neutrino, Belle II and STCF can also provide leading constraints. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, we propose searching for a heavy neutral lepton (HNL), or sterile neutrino, in electron colliders. By using the monophoton signature, we investigate the constraints on the transition magnetic moment of the HNL, which interacts with Standard Model neutrinos and photons. We find that BESIII, Belle II, and STCF have the ability to probe the parameter space of the HNL and study the dipole portal between the electron and tau-neutrino.