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Testing the unitarity of the light neutrino mixing matrix

E. Gabrielli1,2,3, A. Lind4, L. Marzola3,5, K. Müürsepp3,4, and E. Nardi3,4

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Phys. Rev. D 114, 015026 – Published 17 July, 2026

DOI: https://doi.org/10.1103/1fzh-vxp3

Abstract

We propose a novel test of the unitarity of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix at collider experiments. Our approach exploits the incomplete cancellation between t-channel neutrino exchange and s-channel gauge-boson contributions that arises in the presence of violation of the flavor-diagonal PMNS unitarity conditions in weak boson pair production, leading to an anomalous growth of the cross section with energy. Such effects are generic in extensions of the Standard Model in which light neutrinos mix with heavier states, and can manifest at colliders as long as the characteristic energy of the process remains below the mass threshold of the new degrees of freedom. After briefly reviewing these scenarios, we employ our strategy to derive model-independent bounds on flavor diagonal unitarity-violating effects using LEP II data. We then present sensitivity projections for future lepton and hadron colliders, demonstrating that they are well suited to probe the unitarity of the neutrino mixing matrix with this method.

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Outline

Information

Phys. Rev. D 114, 015026– Published 17 July, 2026
  • Received 6 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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