A challenge to lepton universality in B-meson decays

@article{Ciezarek2017ACT,
  title={A challenge to lepton universality in B-meson decays},
  author={Gregory Max Ciezarek and M. Franco Sevilla and Brian Hamilton and Robert Victor Kowalewski and Thomas Kuhr and Vera L{\"u}th and Yutaro Sato},
  journal={Nature},
  year={2017},
  volume={546},
  pages={227-233}
}
One of the key assumptions of the standard model of particle physics is that the interactions of the charged leptons, namely electrons, muons and taus, differ only because of their different masses. Whereas precision tests comparing processes involving electrons and muons have not revealed any definite violation of this assumption, recent studies of B-meson decays involving the higher-mass tau lepton have resulted in observations that challenge lepton universality at the level of four standard… 
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A challenge to lepton universality in B meson decays
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