Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic "van der Meer scan" method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented.

The B-s(0)-(B) over bar (0)(s) oscillation frequency Delta m(s) is measured with 36 pb(-1) of data collected in pp collisions at = 7 TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 B-s(0) -> D-s(-) pi(+) and B-s(0) -> D-s(-) pi(+)pi(-)pi(+) signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6 sigma is observed. The measured oscillation frequency is Delta m(s) = 17.63 +/- 0.11 (stat) +/-0.02 (syst)ps(-1) (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

The production of J/psi pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb(-1) collected with the LHCb detector. The production cross-section for pairs with both J/psi in the rapidity range 2 < y(J/psi) < 4.5 and transverse momentum p(T)(J/psi) < 10 GeV/c issigma(J/psi J/psi) = 5.1 +/- 1.0 +/- 1.1 nb,where the first uncertainty is statistical and the second systematic. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.

The relative abundance of the three decay modes B(0)→D(-)K(+), B(0)→D(-)π(+), and B(s)(0)→D(s)(-)π(+) produced in 7 TeV pp collisions at the LHC is determined from data corresponding to an integrated luminosity of 35 pb(-1). The branching fraction of B(0)→D(-)K(+) is found to be B(B(0)→D(-)K(+)) = (2.01 ± 0.18(stat) ± 0.14(syst)) × 10(-4). The ratio of fragmentation fractions f(s)/f(d) is determined through the relative abundance of B(s)(0)→D(s)(-)π(+) to B(0)→D(-)K(+) and B(0)→D(-)π(+), leading to f(s)/f(d) = 0.253 ± 0.017 ± 0.017 ± 0.020, where the uncertainties are statistical, systematic, and theoretical, respectively.

The \( {{{\bar{\it{\Lambda} }}} \left/ {\it{\Lambda} } \right.} \) and \( {{{\bar{\it{\Lambda} }}} \left/ {{K_S^0}} \right.} \) production ratios are measured by the LHCb detector from 0.3 nb−1 of pp collisions delivered by the LHC at \( \sqrt {s} = 0.9 \) TeV and 1.8 nb−1 at \( \sqrt {s} = 7 \) TeV. Both ratios are presented as a function of transverse momentum, p T, and rapidity, y, in the ranges 0.15 < p T < 2.50 GeV/c and 2.0 < y < 4.5. Results at the two energies are in good agreement as a function of rapidity loss, ∆y = y beam − y, and are consistent with previous measurements. The ratio \( {{{\bar{\it{\Lambda} }}} \left/ {\it{\Lambda}} \right.} \), measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted in simulation, particularly at high rapidity. The ratio \( {{{\bar{\it{\Lambda}}}} \left/ {{K_S^0}} \right.} \), measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.

Using data collected with the LHCb detector in proton-proton collisions at a centreof-mass energy of 7 TeV, the hadronic decay B s → J/ψf0(980) is observed. This CP eigenstate mode could be used to measure mixing-induced CP violation in the B s system. Using a fit to the π π mass spectrum with interfering resonances gives Rf0/φ ≡ Γ(B s →J/ψf0, f0→ππ) Γ(B0 s →J/ψφ, φ→K+K−) = 0.252 −0.032−0.033. In the interval ±90 MeV around 980 MeV, corresponding to approximately two full f0 widths we also find R ′ ≡ Γ(B s→J/ψππ, |m(ππ)−980 MeV|<90 MeV) Γ(B0 s →J/ψφ, φ→K+K−) = 0.162 ± 0.022 ± 0.016, where in both cases the uncertainties are statistical and systematic, respectively.

A search for the decays Bs-->mumu and Bd-->mumu is performed with about 37 pb^{-1} of pp collisions at sqrt{s} = 7 TeV collected by the LHCb experiment at the Large Hadron Collider at CERN. The observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching ratios are BR(Bs-->mumu) < 5.6 x 10^{-8} and BR(Bd-->mumu) <1.5 x 10^{-8} at 95% confidence level.

Branching fractions of the decays ${H}_{b}\ensuremath{\rightarrow}{H}_{c}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ relative to ${H}_{b}\ensuremath{\rightarrow}{H}_{c}{\ensuremath{\pi}}^{\ensuremath{-}}$ are presented, where ${H}_{b}$ (${H}_{c}$) represents ${\overline{B}}^{0}$ (${D}^{+}$), ${B}^{\ensuremath{-}}$ (${D}^{0}$), ${\overline{B}}_{s}^{0}$ (${D}_{s}^{+}$), and ${\ensuremath{\Lambda}}_{b}^{0}$ (${\ensuremath{\Lambda}}_{c}^{+}$). The measurements are performed with the LHCb detector using $35\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of data collected at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$. The ratios of branching fractions are measured to be $[\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]/[\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]=2.38\ifmmode\pm\else\textpm\fi{}0.11\ifmmode\pm\else\textpm\fi{}0.21$, $[\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]/[\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{\ensuremath{-}})]=\phantom{\rule{0ex}{0ex}}1.27\ifmmode\pm\else\textpm\fi{}0.06\ifmmode\pm\else\textpm\fi{}0.11$, $[\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]/[\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]=2.01\ifmmode\pm\else\textpm\fi{}0.37\ifmmode\pm\else\textpm\fi{}0.20$, $[\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\phantom{\rule{0ex}{0ex}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]/[\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})]=1.43\ifmmode\pm\else\textpm\fi{}0.16\ifmmode\pm\else\textpm\fi{}0.13$ We also report measurements of partial decay rates of these decays to excited charm hadrons. These results are of comparable or higher precision than existing measurements.

We present the results of a search for the rare flavor-changing neutral-current decays B → πl^+ l^- (π = π^±, π^0 and l = e, μ) and B^0 → ηl^+ l^- using a sample of e^+ e^- → Υ(4S) → BB decays corresponding to 428  fb^(-1) of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of B(B → πl^+ l^-)<5.9 × 10^(-8) and a lepton-flavor averaged upper limit of B(B0 → ηl^+ l^-) < 6.4 × 10^(-8), both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes B^+ → π^+ e^+ e^-, B^0 → π^0 e^+ e^-, B^+ → π^+ μ^+ μ^-, B^0 → π^0 μ^+ μ^-, B^0 → ηe^+ e^-, and B^0 → ημ^+ μ^-.

Using data collected with the LHCb detector in proton-proton collisions at a centre-ofmass energy of 7 TeV, the semileptonic decays B 0 s → D + s Xμ ν and B 0 s → D KXμν are detected. Two structures are observed in the DK mass spectrum at masses consistent with the known Ds1(2536) + and D s2(2573) + mesons. The measured branching fractions relative to the total B 0 s semileptonic rate are B(B 0 s → D ∗+ s2 Xμ ν)/B(B 0 s → Xμ ν) = (3.3± 1.0± 0.4)%, and B(B 0 s → D + s1Xμ ν)/B(B 0 s → Xμ ν) = (5.4± 1.2± 0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D s2 state in B 0 s decays; we also measure its mass and width.

Branching fractions of the decays H{sub b}{yields}H{sub c}{pi}{sup -}{pi}{sup +}{pi}{sup -} relative to H{sub b}{yields}H{sub c}{pi}{sup -} are presented, where H{sub b} (H{sub c}) represents B{sup 0} (D{sup +}), B{sup -} (D{sup 0}), B{sub s}{sup 0} (D{sub s}{sup +}), and {Lambda}{sub b}{sup 0} ({Lambda}{sub c}{sup +}). The measurements are performed with the LHCb detector using 35 pb{sup -1} of data collected at {radical}(s)=7 TeV. The ratios of branching fractions are measured to be [B(B{sup 0}{yields}D{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{sup 0}{yields}D{sup +}{pi}{sup -})]=2.38{+-}0.11{+-}0.21, [B(B{sup -}{yields}D{sup 0}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{sup -}{yields}D{sup 0}{pi}{sup -})]= 1.27{+-}0.06{+-}0.11, [B(B{sub s}{sup 0}{yields}D{sub s}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{sub s}{sup 0}{yields}D{sub s}{sup +}{pi}{sup -})]=2.01{+-}0.37{+-}0.20, [B({Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -} {pi}{sup +}{pi}{sup -})]/[B({Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -})]=1.43{+-}0.16{+-}0.13 We also report measurements of partial decay rates of these decays to excited charm hadrons. These results are of comparable or higher precision than existing measurements.

R. Aaij, B. Adeva, M. Adinolfi, C. Adrover, A. Affolder, Z. Ajaltouni, J. Albrecht, F. Alessio, M. Alexander, G. Alkhazov, P. Alvarez Cartelle, A.A. Alves Jr, S. Amato, Y. Amhis, J. Anderson, R. B. Appleby, O. Aquines Gutierrez, F. Archilli, L. Arrabito, A. Artamonov, M. Artuso, E. Aslanides, G. Auriemma, S. Bachmann, J. J. Back, D. S. Bailey, V. Balagura, W. Baldini, R. J. Barlow, C. Barschel, S. Barsuk, W. Barter, A. Bates, C. Bauer, Th. Bauer, A. Bay, I. Bediaga, K. Belous, I. Belyaev, E. Ben-Haim, M. Benayoun, G. Bencivenni, S. Benson, J. Benton, R. Bernet, M.-O. Bettler, M. van Beuzekom, A. Bien, S. Bifani, A. Bizzeti, P.M. Bjørnstad, T. Blake, F. Blanc, C. Blanks, J. Blouw, S. Blusk, A. Bobrov, V. Bocci, A. Bondar, N. Bondar, W. Bonivento, S. Borghi, A. Borgia, T. J. V. Bowcock, C. Bozzi, T. Brambach, J. van den Brand, J. Bressieux, D. Brett, S. Brisbane, M. Britsch, T. Britton, N.H. Brook, H. Brown, A. Büchler-Germann, I. Burducea, A. Bursche, J. Buytaert, S. Cadeddu, J.M. Caicedo Carvajal, O. Callot, M. Calvi, M. Calvo Gomez, A. Camboni, P. Campana, A. Carbone, G. Carboni, R. Cardinale, A. Cardini, L. Carson, K. Carvalho Akiba, G. Casse, M. Cattaneo, M. Charles, Ph. Charpentier, N. Chiapolini, K. Ciba, X. Cid Vidal, G. Ciezarek, P. E. L. Clarke, M. Clemencic, H. V. Cliff, J. Closier, C. Coca, V. Coco, J. Cogan, P. Collins, F. Constantin, G. Conti, A. Contu, A. Cook, M. Coombes, G. Corti, G.A. Cowan, R. Currie, B. D’Almagne, C. D’Ambrosio, P. David, I. De Bonis, S. De Capua, M. De Cian, F. De Lorenzi, J.M. De Miranda, L. De Paula, P. De Simone, D. Decamp, M. Deckenhoff, H. Degaudenzi, M. Deissenroth, L. Del Buono, C. Deplano, O. Deschamps, F. Dettori, J. Dickens, H. Dijkstra, P. Diniz Batista, S. Donleavy, F. Dordei, A. Dosil Suárez, D. Dossett, A. Dovbnya, F. Dupertuis, R. Dzhelyadin, C. Eames, S. Easo, U. Egede, V. Egorychev, S. Eidelman, D. van Eijk, F. Eisele, S. Eisenhardt, R. Ekelhof, L. Eklund, Ch. Elsasser, D.G. d’Enterria, D. Esperante Pereira, L. Estève, A. Falabella, E. Fanchini, C. Färber, G. Fardell, C. Farinelli, S. Farry, V. Fave, V. Fernandez Albor, M. Ferro-Luzzi, S. Filippov, C. Fitzpatrick, M. Fontana, F. Fontanelli, R. Forty, M. Frank, C. Frei, M. Frosini, S. Furcas, A. Gallas Torreira, D. Galli, M. Gandelman, P. Gandini, Y. Gao, J-C. Garnier, J. Garofoli, J. Garra Tico, L. Garrido, C. Gaspar, N. Gauvin, M. Gersabeck, T. Gershon, Ph. Ghez, V. Gibson, V.V. Gligorov, C. Göbel, D. Golubkov, A. Golutvin, A. Gomes, H. Gordon, M. Grabalosa Gándara, R. Graciani Diaz, L. A. Granado Cardoso, E. Graugés, G. Graziani, A. Grecu, S. Gregson, B. Gui, E. Gushchin, Yu. Guz, T. Gys, G. Haefeli, C. Haen, S. C. Haines, T. Hampson, S. Hansmann-Menzemer, R. Harji, N. Harnew, J. Harrison, P. F. Harrison, J. He, V. Heijne, K. Hennessy, P. Henrard, J. A. Hernando Morata, E. van Herwijnen, E. Hicks, W. Hofmann, K. Holubyev, P. Hopchev, W. Hulsbergen, P. Hunt, T. Huse, R. S. Huston, D. Hutchcroft, D. Hynds, V. Iakovenko, P. Ilten, J. Imong, R. Jacobsson, A. Jaeger, M. Jahjah Hussein, E. Jans, F. Jansen, P. Jaton, B. Jean-Marie, F. Jing, M. John, D. Johnson, C. R. Jones, B. Jost, S. Kandybei, M. Karacson, T.M. Karbach, J. Keaveney, U. Kerzel, T. Ketel, A. Keune, B. Khanji, Y.M. Kim, M. Knecht, S. Koblitz, P. Koppenburg, A. Kozlinskiy, L. Kravchuk, K. Kreplin, M. Kreps, G. Krocker, P. Krokovny, F. Kruse, K. Kruzelecki, M. Kucharczyk, S. Kukulak, R. Kumar, T. Kvaratskheliya, V.N. La Thi, D. Lacarrere, G. Lafferty, A. Lai, D. Lambert, R.W. Lambert, E. Lanciotti, G. Lanfranchi, C. Langenbruch, T. Latham, R. Le Gac, J. van Leerdam, J.-P. Lees, R. Lefèvre, A. Leflat, J. Lefrançois, O. Leroy, T. Lesiak, L. Li, L. Li Gioi, M. Lieng, M. Liles, R. Lindner, C. Linn, B. Liu, G. Liu, J. H. Lopes, E. Lopez Asamar, N. Lopez-March, J. Luisier, F. Machefert, I. V. Machikhiliyan, F. Maciuc, O. Maev, J. Magnin, S. Malde, R.M.D. Mamunur, G. Manca, G. Mancinelli, N. Mangiafave, U. Marconi, R. Märki, J. Marks, G. Martellotti, A. Martens, L. Martin, A. Martı́n Sánchez, D. Martinez Santos, D. Martins Tostes, A. Massafferri, Z. Mathe, C. Matteuzzi, M. Matveev, E. Maurice, B. Maynard, A. Mazurov, G. McGregor, R. McNulty, C. Mclean, M. Meissner, M. Merk, J. Merkel, R. Messi, S. Miglioranzi, D.A. Milanes, M.-N. Minard, J. Molina Rodriguez, S. Monteil, D. Moran, P. Morawski, R. Mountain, I. Mous, F. Muheim, K. Müller, R. Muresan, B. Muryn, M.Musy, J. Mylroie-Smith, P. Naik, T. Nakada, R. Nandakumar, J. Nardulli, I. Nasteva, M. Nedos, M. Needham, N. Neufeld, C. Nguyen-Mau, M. Nicol, S. Nies, V. Niess, N. Nikitin, A. Oblakowska-Mucha, V. Obraztsov, S. Oggero, S. Ogilvy, O. Okhrimenko, R. Oldeman, M. Orlandea, J.M. Otalora Goicochea, P. Owen, B. Pal, J. Palacios, M. Palutan, J. Panman, A. Papanestis, M. Pappagallo, C. Parkes, C. J. Parkinson, G. Passaleva, G. D. Patel, M. Patel, S. K. Paterson, G.N. Patrick, C. Patrignani, C. Pavel-Nicorescu, PHYSICAL REVIEW D 84, 112008 (2011)

A model-independent search for direct CP violation in the Cabibbo-suppressed decay D+→K−K+π+ in a sample of approximately 370 000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb−1. The normalized Dalitz plot distributions for D+ and D− are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.1 MoreReceived 18 October 2011DOI:https://doi.org/10.1103/PhysRevD.84.112008This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.© 2011 CERN, for the LHCb

A search for the decays Bs–>mumu and Bd–>mumu is performed with about 37 pb^-1 of pp collisions at sqrts = 7 TeV collected by the LHCb experiment at the Large Hadron Collider at CERN. The observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching ratios are BR(Bs–>mumu) < 5.6 x 10^-8 and BR(Bd–>mumu) <1.5 x 10^-8 at 95

Branching fractions of the decays H-b -> H-c pi(-)pi(+)pi(-) relative to H-b -> H-c pi(-) are presented, where H-b (H-c) represents (B) over bar (0) (D+), B-(D-0), (B) over bar (0)(s) (D-s(+)), and Lambda(0)(b) (Lambda(+)(c)). The measurements are performed with the LHCb detector using 35 pb(-1) of data collected at root s = 7 TeV. The ratios of branching fractions are measured to be [B (B) over bar -> D+pi(-)pi(+)pi(-))]/[B((B) over bar (0)-> D+pi(-))] = 2.38 +/- 0.11 +/- 0.21, [B(B- -> D-0 pi(-)pi(+)pi(-))]/[B(B- -> D-0 pi(-))] = 1.27 +/- 0.06 +/- 0.11, [B((B) over bar (0)(s) -> D-s(+)pi(-)pi(+)pi(-))]/[B((B) over bar (0)(s) -> D-s(+)pi(-))] = 2.01 +/- 0.37 +/- 0.20, [B(Lambda(0)(b) ->Lambda(+)(c)pi(-) pi(+)pi(-))]/[B(Lambda(0)(b) ->Lambda(+)(c)pi(-))] = 1.43 +/- 0.16 +/- 0.13 We also report measurements of partial decay rates of these decays to excited charm hadrons. These results are of comparable or higher precision than existing measurements.