Measurement of the branching fraction for the decay BK(892)+ at Belle II

Sumitted to PubDB: 2022-09-20

Category: Conference papers and plots, Visibility: Public

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Authors Seema Choudhury
Date Sept. 20, 2022
Belle II Number BELLE2-CONF-PH-2022-009
Abstract We report a measurement of the branching fraction of BK(892)+ decays, where +=μ+μ or e+e, using electron-positron collisions recorded at an energy at or near the Υ(4S) mass and corresponding to an integrated luminosity of 189 fb1. The data was collected during 2019--2021 by the Belle II experiment at the SuperKEKB e+e asymmetric-energy collider. We reconstruct K(892) candidates in the K+π, KS0π+, and K+π0 final states. The signal yields with statistical uncertainties are 22±6, 18±6, and 38±9 for the decays BK(892)μ+μ, BK(892)e+e, and BK(892)+, respectively. We measure the branching fractions of these decays for the entire range of the dilepton mass, excluding the very low mass region to suppress the BK(892)γ(e+e) background and regions compatible with decays of charmonium resonances, to be B(BK(892)μ+μ)=(1.19±0.310.07+0.08)×106,B(BK(892)e+e)=(1.42±0.48±0.09)×106,B(BK(892)+)=(1.25±0.300.07+0.08)×106, where the first and second uncertainties are statistical and systematic, respectively. These results, limited by sample size, are the first measurements of BK(892)+ branching fractions from the Belle II experiment.

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