Estimating JUNO’s Sensitivity to Solar Neutrino-to-antineutrino Conversion and Neutrino Magnetic Moments

We investigated JUNO’s sensitivity to a possible conversion of solar neutrinos into antineutrinos via the spin-flavor precession mechanism, and assessed the implications for constraining the neutrino-magnetic moment. Using a sensitivity-based framework appropriate for counting experiments with no prior observations, we derive 90% confidence level ensemble-average sensitivities on the solar antineutrino flux for 1.8–16.8 and 8.0–16.8 MeV. For the entire energy window, the results do not improve the restrictions of other experiments; the relevance occurs in the highest-energy window. In this window, we report a flux of ϕ_lim ≤ 4.01 × 1 0 1 cm⁻² s⁻¹ and a probability of P_{νe → ν¯e} ≤ 2.07 × 1 0⁻⁵, the latter normalized to the ⁸B flux above threshold, Φ_SSM(E > 8 MeV). Assuming transverse solar magnetic fields of B _⊥ = 50 and 100 kG, the corresponding magnetic-moment sensitivities are μ _ν ≤ 7.27 × 10⁻¹¹ μ_B and 3.64 × 10⁻¹¹ μ_B in the high-energy window. These results highlight that JUNO has the potential to achieve sensitivities comparable to the most stringent astrophysical limits; in particular, the high-energy selection (8.0–16.8 MeV) provides a sensitivity that is competitive with current results, while the full-energy window remains primarily limited by near-reactor backgrounds.