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arXiv · 2609.00121

Neutrino Electroweak Couplings and the Neutrino Fog at Belle II

Carlos Henrique de Lima·David McKeen·Afif Omar·Douglas Tuckler
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Abstract

The mono-photon process $e^+e^- \to \gamma+\mathrm{invisible}$ at Belle II probes both invisible new states and the electroweak couplings of neutrinos. In this work, we study the process $e^+e^- \to \gamma\nu\bar{\nu}$, finding that Belle II with the full expected dataset can determine the neutrino-sensitive effective weak mixing angle to a 3.6$\%$ relative statistical precision, competitive with existing neutrino probes at other energy scales. Polarized beams, as proposed for the Chiral Belle upgrade, separate the neutral- and charged-current contributions and provide independent access to each, giving a handle on the chiral structure of the neutrino gauge interactions. The same process is an irreducible background to dark boson searches, producing a neutrino fog once the luminosity exceeds 1 ab$^{-1}$.

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Carlos Henrique de Lima, David McKeen, Afif Omar, Douglas Tuckler. 2026-08-31. Neutrino Electroweak Couplings and the Neutrino Fog at Belle II. https://arxiv.org/abs/2609.00121

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