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  • Open Access

Is dark matter the origin of the B→Kνν¯ excess at Belle II?

Lorenzo Calibbi1,*, Tong Li1,†, Lopamudra Mukherjee1,‡, and Michael A. Schmidt2,§

  • *Contact author: calibbi@nankai.edu.cn
  • †Contact author: litong@nankai.edu.cn
  • ‡Contact author: lopamudra.physics@gmail.com
  • §Contact author: m.schmidt@unsw.edu.au
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Phys. Rev. D 112, 075020 – Published 10 October, 2025

DOI: https://doi.org/10.1103/r2gw-rwzw

Abstract

We present two models of dark matter (DM) that can provide a natural explanation of the excess of B+→K++invisible events with respect to the Standard Model (SM) prediction for B+→K+νν¯, which has been reported by the Belle II Collaboration. Interactions between the dark and the visible sector are mediated by an axionlike particle in one case, by the kinetic mixing between a dark photon and the SM photon in the second case. Both models encompass a light fermion singlet as the DM candidate and can account for the observed DM relic abundance through, respectively, the freeze-in and the freeze-out production mechanism, while simultaneously explaining the Belle II excess.

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Phys. Rev. D 112, 075020– Published 10 October, 2025
  • Received 19 April 2025
  • Accepted 15 September 2025
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