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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). First observation and amplitude analysis of the B- -> D+K-pi(-) decay. Phys. Rev. D, 91(9), 092002–24pp.
Abstract: The B- -> D+K-pi(-) decay is observed in a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. Its branching fraction is measured to be B(B- -> D+K-pi(-)) = (7.31 +/- 0.19 +/- 0.22 +/- 0.39) x 10(-5) where the uncertainties are statistical, systematic and from the branching fraction of the normalization channel B- -> D+pi(-)pi(-), respectively. An amplitude analysis of the resonant structure of the B- -> D+K-pi(-) decay is used to measure the contributions from quasi-two-body B- -> D-0* (2400)K-0(-), B- -> D-2* (2460)K-0(-), and B- -> D-J* (2760)K-0(-) decays, as well as from nonresonant sources. The D-J* (2760)(0) resonance is determined to have spin 1.
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CMS and LHCb Collaborations(Khachatryan, V. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Observation of the rare B-s(0)->mu(+)mu(-) decay from the combined analysis of CMS and LHCb data. Nature, 522(7554), 68–72.
Abstract: The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson (B-s(0)) and the B-0 meson decaying into two oppositely charged muons (mu(+) and mu(-)) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B-s(0)->mu(+)mu(-) and B-0 ->mu(+)mu(-) decays are very rare, with about four of the former occurring for every billion B-s(0) mesons produced, and one of the latter occurring for every ten billion B-0 mesons(1). A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN2 started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb(Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton-proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B-s(0)->mu(+)mu(-) decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B-0 ->mu(+)mu(-) decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B-s(0) and B-0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Search for long-lived particles decaying to jet pairs. Eur. Phys. J. C, 75(4), 152–12pp.
Abstract: A search is presented for long-lived particles with a mass between 25 and 50 GeV/c(2) and a lifetime between 1 and 200 ps in a sample of proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, corresponding to an integrated luminosity of 0.62 fb(-1), collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a standard model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets. No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Study of CP violation in B-/+ -> Dh(-/+) (h = K,pi) with the modes D -> K-/+pi(+/-)pi(0), D -> pi(+)pi(-)pi(0) and D -> K+K-pi(0). Phys. Rev. D, 91(11), 112014–15pp.
Abstract: An analysis of the decays of B--/+ -> DK -/+ and B--/+ -> D pi(-/+) is presented in which the D meson is reconstructed in the three-body final states K--/+pi(+/-)pi(0), pi(+)pi(-)pi(0) and K+K-pi(0). Using data from LHCb corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions, measurements of several CP observables are performed. First observations are obtained of the suppressed Atwood-Dunietz-Soni decay B--/+ -> [pi K-+(+/-)pi(0)](D)pi(-/+) and the quasi-Gronau-London-Wyler decay B--/+ -> [K+K-pi(0)](D)pi(-/+). The results are interpreted in the context of the unitarity triangle angle gamma and related parameters.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the (eta c)(1S) production cross-section in proton-proton collisions via the decay (eta c)(1S) -> p(p)over-bar. Eur. Phys. J. C, 75(7), 311–12pp.
Abstract: The production of the eta(c)(1S) state in protonproton collisions is probed via its decay to the p (p) over bar final state with the LHCb detector, in the rapidity range 2.0 < y < 4.5 and in the meson transverse-momentum range p(T) > 6.5GeV/c. The cross-section for prompt production of eta(c)(1S) mesons relative to the prompt J/psi cross-section is measured, for the first time, to be s sigma(eta c(1S))/sigma J/psi = 1.74 +/- 0.29 +/- 0.28 +/- 0.18(B) at a centre-of-mass energy root s = 7 TeV using data corresponding to an integrated luminosity of 0.7 fb(-1), and s sigma(eta c(1S))/sigma(J/psi) = 1.60 +/- 0.29 +/- 0.25 +/- 0.17(B) at root s = 8 TeV using 2.0 fb(-1). The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the (eta c)(1S) and J/psi decays to the p (p) over bar final state. In addition, the inclusive branching fraction of b-hadron decays into (eta c)(1S) mesons is measured, for the first time, to be B(b -> X-eta c) = (4.88 +/- 0.64 +/- 0.29 +/- 0.67(B)) x10(-3), where the third uncertainty includes also the uncertainty on the J/psi inclusive branching fraction from b-hadron decays. The difference between the J/psi and (eta c)(1S) meson masses is determined to be 114.7 +/- 1.5 +/- 0.1MeV/c(2).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP Violation in B-0 -> J/psi K-S(0) Decays. Phys. Rev. Lett., 115(3), 031601–9pp.
Abstract: Measurements are presented of the CP violation observables S and C in the decays of B-0 and (B) over bar (0) mesons to the J/psi K-S(0) final state. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected B-0 and (B) over bar (0) decays. The analysis of the time evolution of these decays yields S = 0.731 +/- 0.035(stat) +/- 0.020(syst) and C = -0.038 +/- 0.032(stat) +/- 0.005(syst). In the standard model, S equals sin(2 beta) to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Amplitude analysis of B-0 -> (D)over-bar0K(+)pi(-) decays. Phys. Rev. D, 92(1), 012012–24pp.
Abstract: The Dalitz plot distribution of B-0 -> (D) over bar K-0(+)pi(-) decays is studied using a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. The data are described by an amplitude model that contains contributions from intermediate K* (892)(0), K*(1410)(0), K-2*(1430)(0) and D-2(*)(2460)(-) resonances. The model also contains components to describe broad structures, including the K-0(*)(1430)(0) and D-0(*)(2400)(-) resonances, in the K pi S-wave and the D pi S-and P-waves. The masses and widths of the D-0*(2400)(-) and D-2(*)(2460)(-) resonances are measured, as are the complex amplitudes and fit fractions for all components included in the amplitude model. The model obtained will be an integral part of a future determination of the angle gamma of the Cabibbo-Kobayashi-Maskawa quark mixing matrix using B-0 -> DK+pi(-) decays.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Dalitz plot analysis of B-0 -> (D)over-bar(0)pi(+)pi(-) decays. Phys. Rev. D, 92(3), 032002–40pp.
Abstract: The resonant substructures of B-0 --> (D) over bar (0)pi(+)pi(-) decays are studied with the Dalitz plot technique. In this study a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions collected by the LHCb detector is used. The branching fraction of the B-0 --> (D) over bar (0)pi(+)pi(-) decay in the region m((D) over bar (0)pi(+/-)) > 2.1 GeV/c(2) is measured to be (8.46 +/- 0.14 +/- 0.29 +/- 0.40) x 10(-4), where the first uncertainty is statistical, the second is systematic and the last arises from the normalization channel B-0 --> D*(2010)(-)pi(+). The pi(+)pi(-) S-wave components are modeled with the isobar and K-matrix formalisms. Results of the Dalitz plot analyses using both models are presented. A resonant structure at m((D) over bar (0)pi(-)) approximate to 2.8 GeV/c(2) is confirmed and its spin-parity is determined for the first time as J(P) = 3(-). The branching fraction, mass and width of this structure are determined together with those of the D-0*(2400)(-) and D-2*(2460)(-) resonances. The branching fractions of other B-0 --> (D) over bar (0)h(0) decay components with h(0) --> pi(+)pi(-) also reported. Many of these branching fraction measurements are the most precise to date. The first observation of the decays B0 --> (D) over bar (0)f(0)(500), B-0 --> (D) over bar (0)f(0)(980), B-0 --> (D) over bar (0)rho(1450), B-0 --> D-3(*)(2760)(-)pi(+) and the first evidence of B-0 --> (D) over bar (0)f(0)(2020) are presented.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Quantum numbers of the X(3872) state and orbital angular momentum in its rho(0)J/psi decay. Phys. Rev. D, 92(1), 011102–9pp.
Abstract: Angular correlations in B+ -> X(3872)K+ decays, with X(3872) -> rho(0)J/psi, rho(0) -> pi(+)pi(-) and J/psi -> pi(+)pi(-), are used to measure orbital angular momentum contributions and to determine the J(PC) value of the X(3872) meson. The data correspond to an integrated luminosity of 3.0 fb(-1) of proton- proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be J(PC) = 1(++). The X(3872) is found to decay predominantly through an S wave and an upper limit of 4% at 95% C.L. is set on the D-wave contribution.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Observation of the B-0 -> rho(0)rho(0) decay from an amplitude analysis of B-0 -> (pi(+)pi(-))(pi(+)pi(-)) decays. Phys. Lett. B, 747, 468–478.
Abstract: Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb(-1), are analysed to search for the charmless B-0 -> rho(0)rho(0) decay. More than 600 B-0 -> (pi(+)pi(-))(pi(+)pi(-)) signal decays are selected and used to perform an amplitude, analysis, under the assumption of no CP violation in the decay, from which the B-0 -> rho(0)rho(0) decay is observed for the first time with 7.1 standard deviations significance. The fraction of B-0 -> rho(0)rho(0) decays yielding a longitudinally polarised final state is measured to be f(L) = 0.745(-0.058)(+0.048)(stat) +/- 0.034(syst). The B-0 -> rho(0)rho(0) branching fraction, using the B-0 -> phi K*(892)(0) decay as reference, is also reported as B(B-0 -> rho(0)rho(0)) = (0.94 +/- 0.17(stat) +/- 0.09(syst) +/- 0.06(BF)) x 10(-6).
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