# Test of lepton universality with B 0 → K *0 ℓ + ℓ − decays

Aaij, R, Adeva, B, Adinolfi, M, Ajaltouni, Z, Akar, S, Albrecht, J, Alessio, F, Alexander, M, Ali, S, Alkhazov, G
et al (show 780 more authors) (2017) Test of lepton universality with B 0 → K *0 ℓ + ℓ − decays. The Journal of High Energy Physics, 2017 (8).

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## Abstract

A test of lepton universality, performed by measuring the ratio of the branching fractions of the B 0 → K *0 μ + μ − and B 0 → K *0 e + 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/c 2 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, q 2, to be RK∗0={0.66+−0.110.07(stat)±0.03(syst)for0.045<q2<1.1GeV2/c4,0.69+−0.110.07(stat)±0.05(syst)for1.1<q2<6.0GeV2/c4. 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 q 2 regions, respectively.

Item Type: Article B physics, Branching fraction, Hadron-Hadron scattering (experiments), Rare decay Symplectic Admin 11 Sep 2017 12:52 19 Oct 2021 10:14 10.1007/JHEP08(2017)055 Publisher https://livrepository.liverpool.ac.uk/id/eprint/3009391