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Axionlike particles and sterile neutrinos solve the $B \to K ν \bar{ν}$ and $B \to π K$ puzzles

Bhubanjyoti Bhattacharya ^1,*, Alakabha Datta ^2,†, Girish Kumar ^3,‡, and Danny Marfatia^4,§

¹Department of Natural Sciences, Lawrence Technological University, Southfield, Michigan 48075, USA
²Department of Physics and Astronomy, University of Mississippi, Oxford, Mississippi 38677, USA
³Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208, USA
⁴Department of Physics and Astronomy, University of Hawaii, Honolulu, Hawaii 96822, USA

^*Contact author: bbhattach@ltu.edu
^†Contact author: datta@phy.olemiss.edu
^‡Contact author: girish89@sc.edu
^§Contact author: dmarf8@hawaii.edu

Phys. Rev. D 114, 035046 – Published 31 August, 2026

DOI: https://doi.org/10.1103/gd5l-gjrz

Abstract

The recent measurement of the branching ratio of $B^{+} \to K^{+} + inv$ (where “inv” denotes invisible states) by the Belle II Collaboration is enhanced relative to the standard model expectation by $2.7 σ$ . An older puzzle persists in measurements of the branching ratios and $C P$ asymmetries of $B \to π K$ decays. We address these two anomalies in flavor-changing neutral current $B$ decays, with a short-lived axionlike particle (ALP) with mass close to that of the $π^{0}$ . In the model with the minimum number of new couplings, the ALP has couplings to the photon, top quark and a heavy sterile neutrino. The ALP contributes to the $B \to π^{0} K$ decays by mixing with the $π^{0}$ . It contributes to $B^{+} \to K^{+} + inv$ by its off-shell coupling to sterile neutrino pairs. The model can explain the excess in the total rate, but not the observed distribution of signal events. We make predictions for all $B \to K^{(*)} + inv$ modes and for the rare kaon decays, $K^{+} \to π^{+} + inv$ and $K_{L} \to π^{0} + inv$ . We find an appreciable contribution to the magnetic moment of the muon, and negligible contributions to the magnetic moment of the electron and $b \to s e^{+} e^{-}$ .

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References (50)

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Phys. Rev. D 114, 035046– Published 31 August, 2026

Vol. 114, Iss. 3 — 1 August 2026

Received 29 May 2026
Accepted 11 August 2026

DOI: https://doi.org/10.1103/gd5l-gjrz

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Axionlike particles and sterile neutrinos solve the $B \to K ν \bar{ν}$ and $B \to π K$ puzzles

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Axionlike particles and sterile neutrinos solve the B→Kνν¯ and B→πK puzzles

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Axionlike particles and sterile neutrinos solve the $B \to K ν \bar{ν}$ and $B \to π K$ puzzles