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Decoding the B → K ν ν excess at Belle II: Kinematics, operators, and masses

Fridell, Kåre·Ghosh, Mitrajyoti·Okui, Takemichi (ORCID:0000000321945137)·Tobioka, Kohsaku (ORCID:0000000325409649)
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Abstract

An excess in the branching fraction for B + → K + ν ν recently measured at Belle II may be a hint of new physics. We perform thorough likelihood analyses for different new physics scenarios such as B → K X with a new invisible particle X , or B → K χ χ through a scalar, vector, or tensor current with χ being a new invisible particle or a neutrino. We find that vector-current three-body decay with m X ≃ 0.6 GeV—which may be dark matter—is most favored, while two-body decay with m X ≃ 2 GeV is also competitive. The best-fit branching fractions for the scalar and tensor cases are a few times larger than for the two-body and vector cases. Past measurements provide further discrimination, although the best-fit parameters stay similar. Published by the American Physical Society 2024

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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSBottom mesonsDark matterEffective field theoryKaonsLeptonic, semileptonic & radiative decaysNeutrinosRare decaysSignatures with missing energy

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Fridell, Kåre, Ghosh, Mitrajyoti, Okui, Takemichi (ORCID:0000000321945137), Tobioka, Kohsaku (ORCID:0000000325409649). 2024-06-07. Decoding the B → K ν ν excess at Belle II: Kinematics, operators, and masses. https://doi.org/10.1103/physrevd.109.115006

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