LHCb CollaborationAdeva Andany, BernardoBorsato, MartinoChobanova, VeronikaCid Vidal, XabierDosil Suárez, ÁlvaroFernández Prieto, AntonioGarcía Pardiñas, JuliánLemos Cid, EdgarLucio Martínez, MiriamMartínez Santos, DiegoPlo Casasus, MáximoPrisciandaro, JessicaRamos Pernas, MiguelRomero Vidal, AntonioSaborido Silva, Juan JoséSanmartín Sedes, BraisSantamarina Ríos, CibránVázquez Regueiro, PabloVieites Díaz, MaríaVázquez Sierra, Carlos2020-05-282020-05-282017Aaij, R., Adeva, B., Adinolfi, M. et al. Test of lepton universality with B0 → K *0 ℓ + ℓ − decays. J. High Energ. Phys. 2017, 55 (2017). https://doi.org/10.1007/JHEP08(2017)0551029-8479http://hdl.handle.net/10347/22664A 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.eng© CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.https://creativecommons.org/licenses/by/4.0B physicsBranching fractionHadron-Hadron scattering (experiments)Rare decayjournal article10.1007/JHEP08(2017)055open access