Measurements of the branching fraction, isospin asymmetry, and lepton-universality ratio in {\boldmath BJ/ψK} decays at Belle II

Sumitted to PubDB: 2022-07-22

Category: Conference papers and plots, Visibility: Public

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Authors Gagan Mohanty, Saurabh Sandilya, Rahul Tiwary
Non-Belle II authors S. Halder
Date July 21, 2022
Belle II Number BELLE2-CONF-PH-2022-006
Abstract We report a study of BJ/ψ(+)K decays, where represents an electron or a muon, using e+e collisions at the Υ(4S) resonance. The data were collected by the Belle~II experiment at the SuperKEKB asymmetric-energy collider during 2019--2021, corresponding to an integrated luminosity of 189\,fb1. The measured quantities are the branching fractions (B) of the decay channels B+J/ψ(e+e)K+, B+J/ψ(μ+μ)K+, B0J/ψ(e+e)KS0, and B0J/ψ(μ+μ)KS0; the lepton-flavor-dependent isospin asymmetries for the electron [AI(BJ/ψ(e+e)K)] and muon [AI(BJ/ψ(μ+μ)K)] channels; and the ratios of branching fractions between the muon and electron channels for the charged [RK+(J/ψ)] and neutral kaon [RK0(J/ψ)] case. We obtain B(B+J/ψ(e+e)K+)=(6.00±0.10±0.19)×105,B(B+J/ψ(μ+μ)K+)=(6.06±0.09±0.19)×105,B(B0J/ψ(e+e)KS0)=(2.67±0.08±0.12)×105,B(B0J/ψ(μ+μ)KS0)=(2.78±0.08±0.12)×105,AI(BJ/ψ(e+e)K)=0.022±0.016±0.030,AI(BJ/ψ(μ+μ)K)=0.006±0.015±0.030,RK+(J/ψ)=1.009±0.022±0.008, andRK0(J/ψ)=1.042±0.042±0.008, where the first uncertainties are statistical and the second are systematic. The measurements are consistent with the world-average values.

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