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Aaij, R.; Amhis, Y.; Barsuk, S.; Borsato, M.; Kochebina, O.; Lefrançois, J.; Li, Y.; Machefert, F.; Quagliani, R.; Robbe, P.; Schune, M.-H.; Teklishyn, M.; Vallier, A.; Viaud, B.; Wormser, G.; Ajaltouni, Z.J.; Baalouch, M.; Cogneras, E.; Deschamps, O.; El Rifai, I.; Gazzoni, G.; Grabalosa Gándara, M.; Henrard, Pierre; Hoballah, M.; Kozeiha, M.; Lefèvre, R.; Maratas, J.; Monteil, S.; Niess, V.; Perret, P.; Beaucourt, L.; Chefdeville, M.; Decamp, D.; Déléage, N.; Ghez, Ph; Lees, J.-P.; Marchand, J.-F.; Minard, M.-N.; Pietrzyk, B.; Qian, W.; t'Jampens, S.; Tisserand, V.; Tournefier, E.; Akar, S.; Aslanides, E.; Cogan, J.; Kanso, W.; Legac, R.; Leroy, O.; Mancinelli, G.; Martin, M.; Mordà, A.; Serrano, J.; Tayduganov, A.; Tsaregorodtsev, A.
Physical review letters, 2015, Letnik: 115Journal Article
The branching fraction ratio R(D∗)≡B(B¯¯¯0→D∗+τ−ν¯τ)/B(B¯¯¯0→D∗+μ−ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0\invfb of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ−→μ−ν¯μντ. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯¯¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the Standard Model.
