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Choudhury, S.*; 谷田 聖; Belle Collaboration*; 他221名*
Journal of High Energy Physics (Internet), 2021(3), p.105_1 - 105_19, 2021/03
被引用回数:31 パーセンタイル:93.69(Physics, Particles & Fields)We present measurements of the branching fractions for the decays and
, and their ratio (
), using a data sample of 711
that contains
events. The data were collected at the
resonance with the Belle detector at the KEKB asymmetric-energy
collider. The ratio
is measured in five bins of dilepton invariant-mass-squared (
):
,
and (
, along with the whole
region. The
value for
is
. The first and second uncertainties listed are statistical and systematic, respectively. All results for
are consistent with Standard Model predictions. We also measure
-averaged isospin asymmetries in the same
bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the
bin in the mode with muon final states. The measured differential branching fractions,
, are consistent with theoretical predictions for charged
decays, while the corresponding values are below the expectations for neutral
decays. We have also searched for lepton-flavor-violating
decays and set
confidence-level upper limits on the branching fraction in the range of
for
, and
modes.