PoS - Proceedings of Science
Volume 364 - European Physical Society Conference on High Energy Physics (EPS-HEP2019) - Flavour Physics and CP Violation
Measurement of Lepton Flavor Universality in $B$ decays at Belle
S. Choudhury* and  On behalf of the BELLE Collaboration
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Pre-published on: October 11, 2020
Published on: November 12, 2020
We test the lepton flavor universality, $R_{K{^{(\ast)}}}$, in $B \rightarrow K{^{(\ast)}}\ell^{+}\ell^{-}$ ($\ell = e,\mu$) decays using a data sample of $711$ $\rm{fb}^{-1}$ that contains $772 \times 10^{6}$ $B\bar{B}$ events. The data were collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The ratio $R_{K^{\ast}}$ is measured in bins of dilepton invariant-mass squared, $q^{2}$; $>0.045$, [0.1 - 8.0], [15.0 - 19.0], [0.045 - 1.1] and [1.1 - 6.0] ${\rm{GeV}}^{2}/c^{4}$. Similarly, $R_{K}$ is measured in $q^{2}$ bin of [0.1 - 4.0], [4.0 - 8.12], [1.0 - 6.0], $>14.18$ and $>0.1$ ${\rm{GeV}}^{2}/c^{4}$. The results are found to be consistent with SM expectation.
We have also measured the $CP-$averaged isospin asymmetries ($A_{I}$) in different $q^{2}$ bins for $B \rightarrow K\ell^{+}\ell^{-}$ mode. The $A_{I}$ has negative asymmetry for almost all the bins with the largest deviation of 2.7 standard deviations in $q^{2}\in(1.0,6.0)$ ${\rm{GeV}}^{2}/c^{4}$ bin for $B \rightarrow K\mu^{+}\mu^{-}$ channel.
DOI: https://doi.org/10.22323/1.364.0259
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