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The structure dependent radiative K + → e+νγ (KSD+e2γ) decay was investigated with stopped positive kaons. The e+ momentum spectra containing 574±30 KSD+e2γ events with a K + → μ+ν (Kμ2) background of 28 ± 19 events were measured with and without a photon in coincidence and analyzed with Monte Carlo simulations for acceptance and detector response to extract the ratio of the branching ratio of the KSD+e2γ decay and the K + → e+ν decay including the internal bremsstrahlung process (Ke2(γ )). A value of Br(KSD+e2γ )/Br(Ke2(γ )) = 1.12 ± 0.07stat ± 0.04syst was obtained. This indicates a partial branching ratio, Br(KSD+e2γ , pe > 200 MeV/c, Eγ > 10 MeV)/Br(Kμ2) = (1.85 ± 0.11stat ± 0.07syst) × 10−5, which is 25% (∼2.5σ) higher than the previous experimental result.

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APA Citation

Ito, H., Kobayashi, A., S. Bianchin, Cao, T., C. Djalali, D.H. Dongwi, Gautam, T., Gill, D., M.D. Hasinoff, Horie, K., Igarashi, Y., J. Imazato, N. Kalantarians, Kawai, H., Kimura, S., Kodama, S., Kohl, M., Lu, H., O. Mineev, & Monaghan, P. (2022). Measurement of structure dependent radiative K+ → e+νγ decays using stopped positive kaons. Physics Letters. B, 826.