Test of lepton universality with B0 → K*0+ decays

The LHCb Collaboration

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A test of lepton universality, performed by measuring the ratio of the branching fractions of the B0 → K*0μ+μ− and B0 → K*0e+e− decays, RK*0, is presented. The K*0 meson is reconstructed in the final state K+π−, which is required to have an invariant mass within 100 MeV/c2 of the known K*(892)0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q2, to be (Formula presented.) The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of RK*0 to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q2 regions, respectively.
Original languageEnglish
Article number55
Number of pages31
JournalJournal of High Energy Physics
Issue number8
Publication statusPublished - 2017
Externally publishedYes


  • B physics
  • Branching fraction
  • Hadron-Hadron scattering (experiments)
  • Rare decay

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