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arXiv · 2609.38233

XENONnT $pp$-Dominated Solar Neutrinos Constrain the $ν_1$ Pseudo-Dirac Splitting

Gio Leone
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Abstract

XENONnT has measured a low-energy solar-neutrino signal dominated by $pp$ neutrinos. At these energies, an ultra-small pseudo-Dirac mass-squared splitting induces detectable active-sterile oscillations over the Sun--Earth baseline. We study pseudo-Dirac oscillations of the first mass eigenstate, compute the resulting modification of the $pp+{}^7$Be electron-recoil spectrum, and construct a likelihood from the published XENONnT energy spectra. We find that the XENONnT data exclude $5.9\times10^{-13}\,\mathrm{eV}^2\lesssim δm_1^2 \leq 10^{-11}\,\mathrm{eV}^2$ at the $2σ$ level, extending current solar-neutrino sensitivity to smaller mass splittings and approaching a regime previously discussed for future $pp$-sensitive detectors.

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Gio Leone. 2026-10-01. XENONnT $pp$-Dominated Solar Neutrinos Constrain the $ν_1$ Pseudo-Dirac Splitting. https://arxiv.org/abs/2609.38233

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