27 research outputs found

    Determination of gamma and-2 beta(s) from charmless two-body decays of beauty mesons

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    Using the latest LHCb measurements of time-dependent CP violation in the B-s(0) -> K+K- decay, a U-spin relation between the decay amplitudes of B-s(0) -> K+K- and B-0 -> p(+)p(-) decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B-s(0) mixing phase -2 beta(s). Results from an extended approach, which uses additional inputs on B-0 -> pi(0)pi(0) and B+ -> pi(+)pi(0) decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value gamma =( 63.5(-6.7)(+7.2))degrees modulo 180 degrees is determined. In an alternative analysis, the value -2 beta(s)= - 0.12(-0.16)(+ 0.14) rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/)

    Search for the decay D-0 -> pi(+)pi(-)mu(+)mu(-)

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    A search for the D-0 -> pi(+)pi(-)mu(+)mu(-) decay, where the muon pair does not originate from a resonance, is performed using proton-proton collision data corresponding to an integrated luminosity of 1.0 fb(-1) recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D-0 -> pi(+)pi(-)phi(-> mu(+)mu(-)), under the assumption of a phase-space model, is found to be B(D-0 -> pi(+)pi(-)mu(+)mu(-))/B(D-0 -> pi(+)pi(-)phi(-> mu(+)mu(-))) pi(+)pi(-)mu(+)mu(-)) < 5.5 x 10(-7) at 90% confidence level. This is the most stringent to date

    Precision measurement of the ratio of the Lambda(0)(b) to (B)over-bar(0) lifetimes

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    The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the (B) over bar (0) lifetime, the Lambda(0)(b) lifetime is found to be 1.479 +/- 0.009 +/- 0.010 ps. (C) 2014 The Authors. Published by Elsevier B.V

    Measurement of the CP-violating phase beta in B-0 -> J/psi pi(+)pi(-) decays and limits on penguin effects

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    Time-dependent CP violation is measured in the (B-0) over bar -> J/psi pi(+)pi(-) p-channel for each pi(+)pi(-) resonant final state using data collected with an integrated luminosity of 3.0 fb(-1) in pp collisions using the LHCb detector. The final state with the largest rate, J/psi rho(0)(770), is used to measure the CP-violating angle 2 beta(eff) to be (41.7 +/- 9.6(-6.3)(+2.8)).. This result can be used to limit the size of penguin amplitude contributions to CPviolation measurements in, for example, (B-0) over bar -> J/psi pi(+)pi(-) decays. Assuming approximate SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the CP-violating phase phi(s) limited to be within the interval [-1.05 degrees, + 1.18 degrees] at 95% confidence level. Changes to the limit due to SU(3) symmetry breaking effects are also discussed. (C) 2015 The Authors. Published by Elsevier B.V

    Study of the rare B-s(0) and B-0 decays into the pi(+) pi(-) mu(+) mu(-) final state

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    A search for the rare decays B-s(0) -> pi(+) pi-mu(+) mu-and B-0 -> pi(+) pi-mu(+) mu-is performed in a data set corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3GeV/c(2) and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B-s(0) -> pi(+) pi-mu(+) mu- and the first evidence of the decay B-0 -> pi(+) pi-mu(+) mu-are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(B-s(0) -> pi(+) pi-mu(+) mu(-)) =(8.6 +/- 1.5(stat) +/- 0.7(syst) +/- 0.7 (norm)) x 10(-8) and B(B-0 -> pi(+) pi-mu(+) mu(-)) =(2.11 +/- 0.51(stat) +/- 0.15(syst) +/- 0.16(norm)) x10(-8), where the third uncertainty is due to the branching fraction of the decay B-0. -> J/Psi(mu(+) mu(-)) K*(892)(0)(-> K+ pi(-)), used as a normalisation. (C) 2015 The Authors. Published by Elsevier B.V

    Evidence for the decay X(3872) -> psi(2S)gamma

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    Evidence for the decay mode X(3872) -> psi(2S)gamma in B+ -> X(3872)K+ decays is found with a significance of 4.4 standard deviations. The analysis is based on a data sample of proton proton collisions, corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb detector, at centre-of-mass energies of 7 and 8 TeV. The ratio of the branching fraction of the X(3872) -> psi(2S)gamma decay to that of the X(3872) -> J/psi gamma decay is measured to be B(X(3872) -> psi(2S)gamma)/B(X(3872) -> J/psi gamma) = 2.46 +/- 0.64 +/- 0.29, where the first uncertainty is statistical and the second is systematic. The measured value does not support a pure D (D) over bar* molecular interpretation of the X(3872) state. (C) 2014 CERN for the benefit of the LHCb Collaboration. Published by Elsevier B.V

    A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states

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    A first study of CP violation in the decay modes B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-) and B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-), where h labels a K or pi meson and D labels a D-0 or (D) over bar (0) meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb(-1). The analysis is sensitive to the CP-violating CKM phase gamma through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of gamma using other decay modes. (C) 2014 The Authors. Published by Elsevier B.V

    LHCb detector performance

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    The LHCb detector is a forward spectrometer at the Large Hadron Collider (LHC) at CERN. The experiment is designed for precision measurements of CP violation and rare decays of beauty and charm hadrons. In this paper the performance of the various LHCb sub-detectors and the trigger system are described, using data taken from 2010 to 2012. It is shown that the design criteria of the experiment have been met. The excellent performance of the detector has allowed the LHCb collaboration to publish a wide range of physics results, demonstrating LHCb's unique role, both as a heavy flavour experiment and as a general purpose detector in the forward region

    Identification of beauty and charm quark jets at LHCb

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    Identification of jets originating from beauty and charm quarks is important for measuring Standard Model processes and for searching for new physics. The performance of algorithms developed to select b- and c-quark jets is measured using data recorded by LHCb from proton-proton collisions at root s = 7TeV in 2011 and at root s = 8TeV in 2012. The efficiency for identifying a b (c) jet is about 65%(25%) with a probability for misidentifying a light-parton jet of 0.3% for jets with transverse momentum pT > 20GeV and pseudorapidity 2 : 2 < eta < 4.2. The dependence of the performance on the pT and eta of the jet is also measured

    Measurement of the lifetime of the B-c(+) meson using the B-c(+) -> J/psi pi(+) decay mode

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    The difference in total widths between the B-c(+) and B+ mesons is measured using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of B-c(+) -> J/psi pi(+) and B+ -> J/psi K+ decays, the width difference is measured to be Delta Gamma = Gamma(Bc+) - Gamma(Bc+) = 4.46 +/- 0.14 +/- 0.07 mm(-1) c, where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B-c(+) clifetime, tau(Bc+) = 513.4 +/- 11.0 +/- 5.7 fs, where the first uncertainty is statistical and the second is systematic. (C) 2015 The Authors. Published by Elsevier B.V
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