LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of B-c(+) -> J/ psi D-s(+) and B-c(+) -> J/ psi D-s*(+) decays. Phys. Rev. D, 87(11), 112012–10pp.
Abstract: The decays B-c(+) -> J/ psi D-s(+) and B-c(+) -> J/ psi D-s*(+) are observed for the first time using a dataset, corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of root s = 7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be 'B(B-c(+) -> J/ psi D-s(+))/B(B-c(+) -> J/ psi pi(+)) = 2.90 +/- 0.57 +/- 0.24, B(B-c(+) -> J/psi D-s*(+))/B(B-c(+) -> J/ psi D-s(+)) = 2.37 +/- 0.56 +/- 0.10, where the first uncertainties are statistical and the second systematic. The mass of the B-c(+) meson is measured to be m(Bc+) = 6276.28 +/- 1.44(stat) +/- 0.36(syst) MeV/c(2), using the B-c(+) -> J/ psi D-s(+) decay mode.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Measurement of CP violation and the B-s(0) meson decay width difference with B-s(0) -> J/psi K+K- and B-s(0) -> J/psi pi(+) pi(-)decays. Phys. Rev. D, 87(11), 112010–21pp.
Abstract: The time-dependent CP asymmetry in B-s(0) -> J/psi K+ K- decays is measured using pp collision data at root s = 7 TeV, corresponding to an integrated luminosity of 1: 0 fb(-1), collected with the LHCb detector. The decay-time distribution is characterized by the decay widths Gamma(L) and Gamma(H) of the light and heavy mass eigenstates of the B-s(0) – (B) over barB(s)(0) system and by a CP-violating phase s. In a sample of 27 617 B-s(0) -> J/psi K+ K- decays, where the dominant contribution comes from B-s(0) -> J/psi K+ K- decays, these parameters are measured to be phi(s) = 0. 07 +/- 0.09(stat) +/- 0. 01(syst) rad, Gamma(s) equivalent to (Gamma(L) + Gamma(L))/2 = 0.663 +/- 0.005(stat) +/- 0.006(syst) ps(-1), and 0.006(syst) ps(-1), and Delta Gamma(s) equivalent to Gamma(L) – Gamma(L) = 0.100 +/- 0.016(stat) +/- 0.003(syst) ps(-1), corresponding to the single most precise determination of phi(s), Delta Gamma(s), and Gamma(s.). The result of performing a combined analysis with B-s(0) -> J/psi pi(+) pi(-) decays gives phi(s) = 0.01 +/- 0.07(stat) +/- 0.01(syst)rad, Gamma(s) = 0.661 +/- 0.004(stat) +/- 0.006(syst) ps(-1), and Delta Gamma(s) = 0.106 +/- 0.011(stat) +/- 0.007(syst) ps(-1). All measurements are in agreement with the Standard Model predictions.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Measurement of the branching fractions of the decays B-s(0) -> (D)over-bar(0)K(-) pi(+) and B-0 -> (D)over-bar(0)K(+) pi(-). Phys. Rev. D, 87(11), 112009–10pp.
Abstract: The first observation of the decay B-s(0) -> (D) over bar K-0(-) pi(+) is reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions, collected with the LHCb detector. The branching fraction relative to that of the topologically similar decay B-0 -> (D) over bar (0)pi(+)pi(-) is measured to be B(B-0 ->(D) over bar K-0(+)pi(-))/B(B-0 ->(D) over bar (0)pi(+)pi(-)) 1.18 +/- 0.05(stat) +/- 0.12(syst). In addition, the relative branching fraction of the decay B-0 -> (D) over bar K-0(+)pi(-) is measured to be B(B-0 ->(D) over bar K-0(+)pi(-))/B(B-0 ->(D) over bar (0)pi(+)pi(-)) = 0.106 +/-(stat) +/- 0.008(syst).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Measurement of CP-violating asymmetries in B-0 -> (rho pi)(0) decays using a time-dependent Dalitz plot analysis. Phys. Rev. D, 88(1), 012003–26pp.
Abstract: We present results for a time-dependent Dalitz plot measurement of CP-violating asymmetries in the mode B-0 -> pi(+)pi(-)pi(0). The data set is derived from the complete sample of 471 x 10(6) B (B) over bar meson pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at the SLAC National Accelerator Laboratory operating on the Upsilon(4S) resonance. We extract parameters describing the time-dependent B-0 -> rho pi decay probabilities and CP asymmetries, including C = 0.016 +/- 0.059 +/- 0.036, Delta C = 0.234 +/- 0.061 +/- 0.048, S = 0.053 +/- 0.081 +/- 0.034, and Delta S = 0.054 +/- 0.082 +/- 0.039, where the uncertainties are statistical and systematic, respectively. We perform a two-dimensional likelihood scan of the direct CP-violation asymmetry parameters for B-0 -> rho(+/-)pi(-/+) decays, finding the change in chi(2) between the minimum and the origin (corresponding to no direct CP violation) to be Delta chi(2) = 6.42. We present information on the CP-violating parameter alpha in a likelihood scan that incorporates B-+/- -> rho pi measurements. To aid in the interpretation of our results, statistical robustness studies are performed to assess the reliability with which the true values of the physics parameters can be extracted. Significantly, these studies indicate that alpha cannot be reliably extracted with our current sample size, though the other physics parameters are robustly extracted.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for D-(s)(+) -> pi(+)mu(+)mu(-) and D-(s)(+) -> pi(-)mu(+)mu(+) decays. Phys. Lett. B, 724(4-5), 203–212.
Abstract: A search for non-resonant D-(s)(+) -> pi(+)mu(+)mu(-) and D-(s)(+) -> pi(-)mu(+)mu(+) decays is performed using protonproton collision data, corresponding to an integrated luminosity of 1.0 fb(-1), at root s = 7 TeV recorded by the LHCb experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are found to be B(D+ -> pi(+)mu(+)mu(-)) < 7.3 (8.3) x 10(-8), B(D-s(+) -> pi(+)mu(+)mu(-)) < 4.1 (4.8) x 10(-7), B(D-s(+) -> pi(+)mu(+)mu(-)) < 2.2 (2.5) x 10(-8), B(D-s(+) -> pi(+)mu(+)mu(-)) < 1.2 (1.4) x 10(-7). These limits are the most stringent to date.
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