A new experimental result finds a local 2.6 sigma deviation from the Standard Model expectation of charged lepton universality in particular kinds of B meson decays. But, after considering look elsewhere effects, it is consistent with the Standard Model. Thus, it tends to disprove the case for charged lepton non-universality from several over measurements that are individually not that notable, but collectively seem to have significance. But, it doesn't do so very strongly.
We present a measurement of angular observables and a test of lepton flavor universality in theBelle Collaboration, "Lepton-Flavor-Dependent Angular Analysis of B→K∗ℓ+ℓ−" (December 15, 2016).
B→K∗ℓ+ℓ−decay, where ℓis either eor μ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb−1containing 772×106 BB¯pairs, collected at the Υ(4S)resonance with the Belle detector at the asymmetric-energy e+e−collider KEKB. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.
Other experiments looking for lepton universality violations are reviewed here.
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