Joint explanation of the $B\to \pi K$ puzzle and the $B\to K\nu \overline{\nu }$ excess

Journal Article · 29 April 2025 · Physical Review. D.

DOI: https://doi.org/10.1103/PhysRevD.111.075029 · OSTI ID:2563455

Altmannshofer, W. ; Roy, S.

In light of the recent branching fraction measurement of the $B^{+}\to K^{+}\nu \overline{\nu }$ decay by Belle II and its poor agreement with the Standard Model expectation, we analyze the effects of an axionlike particle (ALP) in $B$ meson decays. We assume a long-lived ALP with a mass of the order of the pion mass that decays to two photons. We focus on a scenario where the ALP decay length is of the order of meters such that the ALP has a non-negligible probability to decay outside the detector volume of Belle II, mimicking the $B^{+}\to K^{+}\nu \overline{\nu }$ signal. Remarkably, such an arrangement is also relevant for the long-standing $B\to \pi K$ puzzle by noting that the measured $B^0\to {\pi }^0{K}^0$ and $B^{+}\to {\pi }^0{K}^{+}$ decays could have a $B^0\to a{K}^0$ and $B^{+}\to a{K}^{+}$ component, respectively. We also argue based on our results that the required ALP-photon effective coupling belongs to a region of parameter space that can be extensively probed in future beam dump experiments like SHiP. Published by the American Physical Society 2025

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0010107
• OSTI ID: 2563455
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 7 Vol. 111; ISSN PRVDAQ; ISSN 2470-0010
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English