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  • Open Access

Hadronic probes of nonstandard neutrino interactions

Carlos Henrique de Lima1,*, David McKeen1,†, John Ng1,‡, and Douglas Tuckler1,2,§

  • 1TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
  • 2Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

  • *Contact author: cdelima@triumf.ca
  • †Contact author: mckeen@triumf.ca
  • ‡Contact author: misery@triumf.ca
  • §Contact author: dtuckler@triumf.ca
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Phys. Rev. D 113, 095016 – Published 7 May, 2026

DOI: https://doi.org/10.1103/73y7-7zv5

Abstract

In this work, we study leptonic decays of hadrons as probes of light neutrinophilic scalars that mediate enhanced neutrino self-interactions. Such scalars can be emitted in processes involving neutrinos, turning two-body decays into three-body final states and producing characteristic spectral distortions. We compute these effects for charged pion decay and nuclear electron capture decay, including both on-shell and off-shell scalar emission, as well as the loop-induced renormalization required to cancel divergences. Using these results, we derive the projected sensitivity of PIONEER and assess the current and future reach of BeEST. The resulting low-energy spectral tails provide a characteristic signal for light neutrinophilic scalars, making upcoming hadron decay experiments powerful probes of light mediators of nonstandard neutrino self-interactions.

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Phys. Rev. D 113, 095016– Published 7 May, 2026
  • Received 3 February 2026
  • Accepted 16 April 2026
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