A Unified Dark Matter Explanation for ${\mathbf{B}}^{+}\to {\mathbf{K}}^{+}\hat{\mathbf{I}}½\overline{\hat{\mathbf{I}}}½$ and the Super-Kamiokande Antineutrino Excess

Abstract

Recent results from Super-Kamiokande and Belle II have revealed intriguing excesses over Standard Model expectations. Super-Kamiokande observes a mild excess of $\bar{\hat{I}}{½}_e^{}$-like events near $20\mathrm{MeV}$, while Belle II reports a branching fraction for $B^{+}\to K^{+}\hat{I}½\bar{\hat{I}}½$ that exceeds the Standard Model prediction by approximately $2.7\ddot{I}ƒ$. In this work, we study the simplest UV-complete complex scalar dark matter model with a gauged $\text{U}(1{)}_{{\text{L}}_{\hat{I}}¼-{\text{L}}_{\ddot{I}}„}^{}$ symmetry. We demonstrate that a light dark sector can simultaneously reproduce the observed dark matter relic density and accommodate both excesses within a unified framework.

6 pages, 2 figures