Observation of $B^0_s$-$\bar{B}^0_s$ mixing and measurement of mixing frequencies using semileptonic B decays
Creators: name: LHCb Collaboration
name: Aaij, R.
name: Adeva, B.
name: Adinolfi, M.
name: Adrover, C.
name: Affolder, A.
name: Ajaltouni, Z.
name: Albrecht, J.
name: Alessio, F.
name: Alexander, M.
name: Ali, S.
name: Alkhazov, G.
name: Cartelle, P. Alvarez
name: Alves, A. A.
name: Amato, S.
name: Amerio, S.
name: Amhis, Y.
name: Anderlini, L.
name: Anderson, J.
name: Andreassen, R.
name: Andrews, J. E.
name: Andrianala, F.
name: Appleby, R. B.
name: Gutierrez, O. Aquines
name: Archilli, F.
name: Artamonov, A.
name: Artuso, M.
name: Aslanides, E.
name: Auriemma, G.
name: Baalouch, M.
name: Bachmann, S.
name: Back, J. J.
name: Baesso, C.
name: Balagura, V.
name: Baldini, W.
name: Barlow, R. J.
name: Barschel, C.
name: Barsuk, S.
name: Barter, W.
name: Bauer, Th.
name: Bay, A.
name: Beddow, J.
name: Bedeschi, F.
name: Bediaga, I.
name: Belogurov, S.
name: Belous, K.
name: Belyaev, I.
name: Ben-Haim, E.
name: Bencivenni, G.
name: Benson, S.
name: Benton, J.
name: Berezhnoy, A.
name: Bernet, R.
name: Bettler, M. -O.
name: van Beuzekom, M.
name: Bien, A.
name: Bifani, S.
name: Bird, T.
name: Bizzeti, A.
name: Bjørnstad, P. M.
name: Blake, T.
name: Blanc, F.
name: Blouw, J.
name: Blusk, S.
name: Bocci, V.
name: Bondar, A.
name: Bondar, N.
name: Bonivento, W.
name: Borghi, S.
name: Borgia, A.
name: Bowcock, T. J. V.
name: Bowen, E.
name: Bozzi, C.
name: Brambach, T.
name: Brand, J. van den
name: Bressieux, J.
name: Brett, D.
name: Britsch, M.
name: Britton, T.
name: Brook, N. H.
name: Brown, H.
name: Burducea, I.
name: Bursche, A.
name: Busetto, G.
name: Buytaert, J.
name: Cadeddu, S.
name: Callot, O.
name: Calvi, M.
name: Gomez, M. Calvo
name: Camboni, A.
name: Campana, P.
name: Perez, D. Campora
name: Carbone, A.
name: Carboni, G.
name: Cardinale, R.
name: Cardini, A.
name: Carranza-Mejia, H.
name: Carson, L.
name: Akiba, K. Carvalho
name: Casse, G.
name: Garcia, L. Castillo
name: Cattaneo, M.
name: Cauet, Ch.
name: Cenci, R.
name: Charles, M.
name: Charpentier, Ph.
name: Chen, P.
name: Chiapolini, N.
name: Chrzaszcz, M.
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Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The $B^0_s$ and $B^0$ mixing frequencies, $Δm_s$ and $Δm_d$, are measured using a data sample corresponding to an integrated luminosity of 1.0 fb^{-1} collected by the LHCb experiment in $pp$ collisions at a centre of mass energy of 7 TeV during 2011. Around 1.8x10^6 candidate events are selected of the type $B^0_{(s)} \to D^-_{(s)} μ^+$ (+ anything), where about half are from peaking and combinatorial backgrounds. To determine the B decay times, a correction is required for the momentum carried by missing particles, which is performed using a simulation-based statistical method. Associated production of muons or mesons allows us to tag the initial-state flavour and so to resolve oscillations due to mixing. We obtain Δm_s = (17.93 \pm 0.22 (stat) \pm 0.15 (syst)) ps^{-1}, Δm_d = (0.503 \pm 0.011 (stat) \pm 0.013 (syst)) ps^{-1}. The hypothesis of no oscillations is rejected by the equivalent of 5.8 standard deviations for $B^0_s$ and 13.0 standard deviations for $B^0$. This is the first observation of $B^0_s$ mixing to be made using only semileptonic decays.