Search for B
Phys Rev Lett
; 127(18): 181802, 2021 Oct 29.
Article
en En
| MEDLINE
| ID: mdl-34767404
ABSTRACT
A search for the flavor-changing neutral-current decay B^{+}âK^{+}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 Ï(4S) resonance and a sample of 9 fb^{-1} collected at an energy 60 MeV 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^{+}âK^{+}νν[over ¯] decay, but also the inclusive properties of the other B meson in the Ï(4S)âBB[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^{+}âK^{+}νν[over ¯] of 4.1×10^{-5} is set at the 90% confidence level.
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En
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Phys Rev Lett
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2021
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Article