1,613 research outputs found

    Measurement of the ratios of branching fractions R(D*) and R(D0)

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    The ratios of branching fractions R ( D ∗ ) ≡ B ( ¯ B → D ∗ τ − ¯ ν τ ) / B ( ¯ B → D ∗ μ − ¯ ν μ ) and R ( D 0 ) ≡ B ( B − → D 0 τ − ¯ ν τ ) / B ( B − → D 0 μ − ¯ ν μ ) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0     fb − 1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ − → μ − ν τ ¯ ν μ . The measured values are R ( D ∗ ) = 0.281 ± 0.018 ± 0.024 and R ( D 0 ) = 0.441 ± 0.060 ± 0.066 , where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ = − 0.43 . The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model

    Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0

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    The B 0 –B 0 oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of 1.0 fb−1 of proton–proton collisions at √ s = 7 TeV, and is found to be Δmd =0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1 . The measurement is based on results from analyses of the decays B 0 → D −π + (D − → K +π −π −) and B 0 → J/ψK ∗0 (J/ψ →μ +μ −,K ∗0 → K +π −) and their charge conjugated modes

    Measurement of the Ratios of Branching Fractions R (D∗) and R (D0)

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    The ratios of branching fractions R(D∗)B(B ̄→D∗τ-ν ̄τ)/B(B ̄→D∗μ-ν ̄μ) and R(D0)B(B-→D0τ-ν ̄τ)/B(B-→D0μ-ν ̄μ) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb-1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ-→μ-ντν ̄μ. The measured values are R(D∗)=0.281±0.018±0.024 and R(D0)=0.441±0.060±0.066, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ=-0.43. The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model

    Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+

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    An analysis of B+ → K0 Sπ+ and B+ → K0 S K+ decays is performed with the LHCb experiment. The pp collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass energies of √ s = 7 TeV and √ s = 8 TeV, respectively. The ratio of branching fractions and the direct CP asymmetries are measured to be B(B+ → K0 S K+ )/B(B+ → K0 Sπ+ ) = 0.064 ± 0.009 (stat.) ± 0.004 (syst.), ACP(B+ → K0 Sπ+ ) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0 S K+ ) = −0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at √ s = 7 TeV is used to search for B+ c → K0 S K+ decays and results in the upper limit ( fc · B(B+ c → K0 S K+ ))/( fu · B(B+ → K0 Sπ+ )) < 5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b quark into a B+ c or a B+ meson, respectively

    Measurement of the D+/- production asymmetry in 7 TeV pp collisions

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    The asymmetry in the production cross-section \sigma of D+/- mesons, A_P = (\sigma(D+) - \sigma(D-))/(\sigma(D+) + \sigma(D-)), is measured in bins of pseudorapidity \eta and transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ -> K_S pi+ decays corresponding to an integrated luminosity of 1.0 fb^-1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 K_S pi+ decay is negligible. No significant dependence on \eta or p_T is observed

    Measurement of the branching fraction ratios R(D+) and R(D*+) using muonic τ decays

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    The branching fraction ratios of B¯ 0 → D+τ−ν¯ τ and B¯ 0 → D+τ−ν¯ τ decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0 fb−1 collected by the LHCb experiment in proton-proton collisions at √s = 13 TeV. The reconstructed final states are formed by combining D+ mesons with τ− → μ−ν¯μντ candidates, where the D+ is reconstructed via the D+ → K−π+π+ decay. The results are R(D+) = 0.249 ± 0.043 ± 0.047, R(D*+) = 0.402 ± 0.081 ± 0.085, where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of −0.39 and are compatible with the standard model

    Measurement of the Ratios of Branching Fractions R(D*) and R(D0)

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    The ratios of branching fractions R(D∗)B(B ̄→D∗τ-ν ̄τ)/B(B ̄→D∗μ-ν ̄μ) and R(D0)B(B-→D0τ-ν ̄τ)/B(B-→D0μ-ν ̄μ) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb-1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ-→μ-ντν ̄μ. The measured values are R(D∗)=0.281±0.018±0.024 and R(D0)=0.441±0.060±0.066, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ=-0.43. The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model

    Measurement of the CP-violating phase phi(s) in (B)over-bar(s)(0) -> J / psi pi(+)pi(-) decays

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    The mixing-induced CP -violating phase ϕs in View the MathML source and View the MathML source decays is measured using the J/ψπ+π− final state in data, taken from 3 fb−1 of integrated luminosity, collected with the LHCb detector in 7 and 8 TeV centre-of-mass pp collisions at the LHC. A time-dependent flavour-tagged amplitude analysis, allowing for direct CP violation, yields a value for the phase ϕs=70±68±8 mrad. This result is consistent with the Standard Model expectation and previous measurements

    Measurement of the time-dependent CP asymmetry in B0 -> J/ψ KS0 decays

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    This Letter reports a measurement of the CP violation observables SJ/ψK0S and CJ/ψK0S in the decay channel B0→J/ψK0S performed with 1.0 fb−1 of pp collisions at s√=7 TeV collected by the LHCb experiment. The fit to the data yields SJ/ψK0S=0.73±0.07(stat)±0.04(syst) and CJ/ψK0S=0.03±0.09(stat)±0.01(syst). Both values are consistent with the current world averages and within expectations from the Standard Model

    Observations of Bºs→ψ(2S)η and Bº(s)→ψ(2S)π+π- decays

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    First observations of the B0s →ψ(2S)η, B0 →ψ(2S)π + π − and B0s →ψ(2S)π + π − decays are made using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in proton–proton collisions at a centre-of-mass energy of √ s = 7 TeV. The ratios of the branching fractions of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are B(B0s →ψ(2S)η) ÷ B(B0s →J/ψη) = 0.83± 0.14 (stat)±0.12 (syst) ±0.02 (B), ; B(B0→ψ(2S)π + π − ) ÷ B(B0→J/ψπ + π − ) = 0.56± 0.07 (stat)±0.05 (syst)± 0.01 (B), ; B(B0s →ψ(2S)π + π − ) ÷ B(B0s →J/ψπ + π − ) = 0.34± 0.04 (stat)±0.03 (syst)± 0.01 (B), where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ and ψ(2S) meson decays
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