Abstract
We consider the sensitivity of the DUNE experiment to a heavy neutral lepton, HNL (also known as sterile neutrino) in the mass range from a few MeV to a few GeV, interacting with the Standard Model via a transition magnetic moment to the active neutrinos, the so-called dipole portal. The HNL is produced via the up-scattering of active neutrinos, and the subsequent decay inside the detector provides a single-photon signal. We show that the tau-neutrino dipole portal can be efficiently probed at the DUNE far detector, using the tau-neutrino flux generated by neutrino oscillations, while the near detector provides better sensitivity to the electron- and muon-neutrino dipole portal. DUNE will be able to explore large regions of currently unconstrained parameter space and has comparable sensitivity to other planned dedicated experiments, such as SHiP. We also comment briefly on the sensitivity to pure HNL mixing with the tau neutrino at the DUNE far detector.
Highlights
Eq (1.1) corresponds to an effective Lagrangian, valid up to a cut-off energy scale Λ, where the transition magnetic moment dα is expected to be of order 1/Λ
We show that the tau-neutrino dipole portal can be efficiently probed at the DUNE far detector, using the tau-neutrino flux generated by neutrino oscillations, while the near detector provides better sensitivity to the electron- and muon-neutrino dipole portal
We show the six-events/year curve for inside and outside events at the DUNE far detector for coherent scattering on nuclei, incoherent scattering on nucleons as well as electrons as a function of the heavy-neutrino mass M4
Summary
The DUNE experiment produces a flux of mostly muon neutrinos with a subleading component of electron neutrinos. If the up-scattering occurs outside the detector in the Earth’s crust or upper mantle, and if the sterile-neutrino mass is low enough, the sterile neutrino will be long lived and can travel through the Earth and decay inside the DUNE far detector (FD) Single-photon production from neutral-current scattering (NC1γ) is expected to have a total cross section ∼ 10−41 cm2/nucleon [32,33,34]. We estimate that this process would induce a background of 0.1 events/year (see [35] for a NC1γ analysis in T2K). The target T can be an electron, proton, neutron, or a nucleus (for coherent interactions)
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