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Report No.

Test of lepton-flavor universality in $${Bto K^astell^+ell^-}$$ decays at Belle

Wehle, S.*; Tanida, Kiyoshi   ; Belle Collaboration*; 179 of others*

We present a measurement of $$R_{K^{ast}}$$, the branching fraction ratio $${{cal B}(Bto K^ast mu^+ mu^-)}$$/ $${{cal B}(Bto K^ast e^+ e^-)}$$, for both charged and neutral $$B$$ mesons. The ratio for the charged case, $$R_{K{^{ast +}}}$$, is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass, $$q^2$$. The analysis is based on a data sample of $$711~mathrm{fb}^{-1}$$, containing $$772times 10^{6}$$ $$Bbar B$$ events, recorded at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider. The obtained results are consistent with Standard Model expectations.



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Category:Physics, Multidisciplinary



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