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Nonunitary solar constraint for long-baseline neutrino experiments

Andrés López Moreno*

  • *Contact author: andres.lopezmoreno@lapp.in2p3.fr
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Phys. Rev. D 113, 113013 – Published 25 June, 2026

DOI: https://doi.org/10.1103/99t8-tl5w

Abstract

Long-baseline neutrino oscillation experiments require external constraints on sin2θ12 and Δm212 to make precision measurements of the leptonic mixing matrix. These constraints come from measurements of the Mikheyev-Smirnov-Wolfenstein (MSW) mixing in solar neutrinos. Here we develop an adiabatic MSW approximation in the presence of heavy neutral leptons; it adds, to leading order, a single new parameter (α11) representing the magnitude of the mixing between the νe state and the heavy sector. We use data from the Borexino, SNO, and KamLAND Collaborations to find a solar constraint appropriate for heavy neutral lepton searches in long-baseline oscillation experiments. Solar data yields a strongly correlated constraint on the solar mass splitting and the magnitude of νe nonunitary mixing, limiting the magnitude of the nonunitary parameter to (1−α11)<0.046 at the 99% credible region.

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Phys. Rev. D 113, 113013– Published 25 June, 2026
  • Received 3 April 2026
  • Accepted 3 June 2026
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Published 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.

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