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Aslanides, E.; Bachmann, S.; Balagura, V.; Ben-Haim, E.; Berninghoff, D.; Betancourt, C.; van Beuzekom, M.; Bezshyiko, Ia; Blanc, F.; Boettcher, T.; Bondar, N.; Bossu, F.; Campora Perez, D. H.; Cid Vidal, X.; Cook, A.; Coombs, G.; Costa Sobral, C. M.; Crocombe, A.; Dall’Occo, E.; De Miranda, J. M.; Dembinski, H. -P.; Dordei, F.; Dosil Suárez, A.; Dovbnya, A.; Dujany, G.; Dziewiecki, M.; Easo, S.; Evans, H. M.; Fernandez Prieto, A.; Fontana, M.; Forshaw, D. C.; Funk, W.; Gascon, D.; Gavardi, L.; Golutvin, A.; Grillo, L.; Han, X.; Henry, L.; Heß, M.; Jiang, F.; John, M.; Johnson, D.; Jones, C. R.; Kariuki, J. M.; Kecke, M.; Khanji, B.; Klimaszewski, K.; Kolpin, M.; Komarov, I.; Kotriakhova, S.; Krokovny, P.; Kuonen, A. K.; Kvaratskheliya, T.; Lanfranchi, G.; Lefèvre, R.; Lemos Cid, E.; Lupato, A.; Marin Benito, C.; Martins Tostes, D.; Meadows, B.; Melnychuk, D.; Merk, M.; Milanes, D. A.; Monteil, S.; Morello, M. J.; Moron, J.; O’Hanlon, D. P.; Oldeman, R.; Pappenheimer, C.; Pastore, A.; Petridis, K.; Petruzzo, M.; Poluektov, A.; Popov, A.; Popov, D.; Potterat, C.; Rademacker, J. H.; Rangel, M. S.; Raven, G.; Rodriguez Perez, P.; Saitta, B.; Sanmartin Sedes, B.; Spaan, B.; Storaci, B.; Tomassetti, L.; Tran, M. T.; Vacca, C.; Vazquez Gomez, R.; Vazquez Regueiro, P.; van Veghel, M.; Verlage, T. A.; Vieira, D.; Vilasis-Cardona, X.; Vollhardt, A.; Wallace, R.; Wilkinson, M.; Wimberley, J.; Wyllie, K.; Zavertyaev, M.; Zhang, Y.
The journal of high energy physics, 08/2017, Letnik: 2017, Številka: 8Journal Article
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, $R_{K^{*0}}$, 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 R K ∗ 0 = { 0.66 − + 0.07 0.11 ( s t a t ) ± 0.03 ( s y s t ) f o r 0.045 < q 2 < 1.1 G e V 2 / c 4 , 0.69 − + 0.07 0.11 ( s t a t ) ± 0.05 ( s y s t ) f o r 1.1 < q 2 < 6.0 G e V 2 / c 4 . 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 $R_{K^{*0}}$ 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.
