Two recent results on rare kaon decays are presented, based on ∼ 2×1011 K± decays recorded by the NA48/2 experiment at CERN SPS in 2003 and 2004. The branching ratio of the rare leptonic decay K± → μ±νμ e+e- has been measured in the region of large e+e- invariant mass Mee ≥140 MeV/c2, where low energy QCD contributions become important and can be calculated in the framework of Chiral Perturbation Theory (ChPT). This branching ratio is measured to be BR(K± → μ±νμ e+e-| Mee ≥ 140 MeV/c2 ) = (7.8±0.2)×10-8. The K± → π±π0e+e- rare decay has been observed for the first time, with about 5000 candidates and a 5% background. The branching ratio in the full kinematic region is measured to be BR(K± → π ±π0e+e-) = (4.22×0.15)×10-6, in good agreement with ChPT-based theoretical predictions.
Model independent measurement of the leptonic kaon decay K± → μ±νμe+e- and study of the K± →π±π0e+e- decay by the NA48/2 experiment / Bizzeti, A.. - In: POS PROCEEDINGS OF SCIENCE. - ISSN 1824-8039. - 2017-:(2017), pp. N/A-N/A. (Intervento presentato al convegno 25th International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2017 tenutosi a University of Birmingham, gbr nel 2017).
Model independent measurement of the leptonic kaon decay K± → μ±νμe+e- and study of the K± →π±π0e+e- decay by the NA48/2 experiment
Bizzeti A.
2017
Abstract
Two recent results on rare kaon decays are presented, based on ∼ 2×1011 K± decays recorded by the NA48/2 experiment at CERN SPS in 2003 and 2004. The branching ratio of the rare leptonic decay K± → μ±νμ e+e- has been measured in the region of large e+e- invariant mass Mee ≥140 MeV/c2, where low energy QCD contributions become important and can be calculated in the framework of Chiral Perturbation Theory (ChPT). This branching ratio is measured to be BR(K± → μ±νμ e+e-| Mee ≥ 140 MeV/c2 ) = (7.8±0.2)×10-8. The K± → π±π0e+e- rare decay has been observed for the first time, with about 5000 candidates and a 5% background. The branching ratio in the full kinematic region is measured to be BR(K± → π ±π0e+e-) = (4.22×0.15)×10-6, in good agreement with ChPT-based theoretical predictions.
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