Measurement of the branching fractions of B\→\η' K decays using 2019/2020 Belle II data

This is the authors' abstract. We don't add key points for this paper.

This note describes the rediscovery of B\→\η' K decays in Belle II data, in the charged and neutral final state: B₀\→\η' KS and^\±\→\η' K^\±. The \η' is searched for in two decay modes:\η'\→\η\π⁺\π⁻ with \η\→\γ\γ, and \η'\→\ρ\γ. analysis uses data collected in 2019 and 2020 at the SuperKEKB asymmetric≠⁺e⁻ collider, with an integrated luminosity of 62.8~fb⁻¹, to $68.2$ million of B̄ pairs produced. The signal yield obtained via an unbinned maximum likelihood fit to signal sensitive, obtaining branching ratios: \(B^\±\→\η'K^\±\) =\(63.4~+3.4-3.3\\,(stat)\\,\±3.2\\,(syst)\\,\) \×10⁻⁶ \(B₀\→\η'KS\) =\(59.9~+5.8-5.5\\,(stat)\\,\±2.9\\,(syst)\\,\) \×10⁻⁶ are consistent with world average.