Abstract
A search for the flavor-changing neutral-current decay B^{+}→K^{+}νν[over ¯] is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The data sample corresponds to an integrated luminosity of 63 fb^{-1} collected at the ϒ(4S) resonance and a sample of 9 fb^{-1} collected at an energy 60MeV below the resonance. Because the measurable decay signature involves only a single charged kaon, a novel measurement approach is used that exploits not only the properties of the B^{+}→K^{+}νν[over ¯] decay, but also the inclusive properties of the other B meson in the ϒ(4S)→BB[over ¯] event, to suppress the background from other B meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of B^{+}→K^{+}νν[over ¯] of 4.1×10^{-5} is set at the 90% confidence level.
Highlights
Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai 200443
The data sample corresponds to an integrated luminosity of 63 fb−1 collected at the Υð4SÞ resonance and a sample of 9 fb−1 collected at an energy 60 MeV below the resonance
K þ ννdecay, and the inclusive properties of the other B meson in the Υð4SÞ → BBevent, to suppress the background from other B meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches
Summary
Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Mexico City 07360. K þ ννdecay, and the inclusive properties of the other B meson in the Υð4SÞ → BBevent, to suppress the background from other B meson decays and light-quark pair production This inclusive tagging approach offers a higher signal efficiency compared to previous searches. In all analyses reported to date, no evidence for a signal is found, and the current experimental upper limit on the branching fraction is estimated to be 1.6 × 10−5 at 90% confidence level [20] In this search, a novel and independent inclusive tagging approach is used, inspired by Ref. The signal and background samples are generated using a variety of event generators, summarized in the
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