27 research outputs found

    Observation of B-s(0) -> chi(c1)phi decay and study of B-0 -> chi K-c1,K-2*(0) decays

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    The first observation of the decay B-s(0) -> chi(c1)phi and a study of B-0 -> chi K-c1,K-2*(0) decays are presented. The analysis is performed using a dataset, corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. The following ratios of branching fractions are measured: B(B-s(0) -> chi(c1)phi)/B(B-s(0) -> J/psi phi) = (18.9 +/- 1.8 (stat) +/- 1.3 (syst) +/- 0.8(B)) x 10(-2), B(B-0 -> chi K-c1*(0))//B(B-0 -> J/psi K*(0)) = (19.8 +/- 1.1 (stat) +/- 1.2 (syst) +/- 0.9(B)) x 10(-2), B(B-0 -> chi K-c2*(0))//B(B-0 -> chi K-c1*(0)) = (17.1 +/- 5.0 (stat) +/- 1.7 (syst) +/- 1.1(B)) x 10(-2), where the third uncertainty is due to the limited knowledge of the branching fractions of chi(c) -> J/psi gamma modes

    Measurement of the flavour-specific CP-violating asymmetry a(sl)(s) in B-s(0) decays

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    The CP-violating asymmetry a(sl)(s), is studied using semileptonic decays of B-s(0) and (B) over bar (0)(s) mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0 fb(-1). The reconstructed final states are D-s(+/-)mu(+/-)(s), with the D-s(+/-) particle decaying in the phi pi(+/-) mode. The D-s(+/-)mu(+/-)(s) yields are summed over B-s(0) and (B) over bar (0)(s) initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain a(sl)(s) = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic

    First measurement of time-dependent CP violation in Bs0→K+K− B_s^0\to K^+K^- decays

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    Direct and mixing-induced CP-violating asymmetries in B-s(0) -> K+K- decays are measured for the first time using a data sample of p p collisions, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C-KK = 0.14 +/- 0.11 +/- 0.03 and S-KK = 0.30 +/- 0.12 +/- 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B-0 -> pi(+)pi(-) decays to be C-pi pi = -0.38 +/- 0.15 +/- 0.02 and S-pi pi = -0.71 +/- 0.13 +/- 0.02, in good agreement with existing measurements

    Model-independent search for CP violation in D-0 > K-K+pi(-)pi(+) and D-0 -> pi(-)pi(+)pi(+)pi(-) decays

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    A search for CP violation in the phase-space structures of 130 and 15 decays to the final states K-K+pi(-)pi(+) and pi(-)pi(+)pi(+)pi(-) is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fb(-1) collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the K-K+pi(-)pi(+) final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the pi(-)pi(+)pi(+)pi(-). final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity

    Measurement of the charge asymmetry in B-+/- -> phi K +/- and search for B-+/- -> phi pi(+/-) decays

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    The CP-violating charge asymmetry in B-+/- -> phi K-+/- decays is measured in a sample of pp collisions at 7 TeV centre-of-mass energy, corresponding to an integrated luminosity of 1.0 fb-1 collected by the LHCb experiment. The result is A(CP)(B-+/- -> phi K-+/-) = 0.022 +/- 0.021 +/- 0.009, where the first uncertainty is statistical and the second systematic. In addition, a search for the B-+/- -> phi pi(+/-) decay mode is performed, using the B-+/- -> phi K-+/- decay rate for normalization. An upper limit on the branching fraction B(B-+/- -> phi pi(+/-)) < 1.5 x 10(-7) is set at 90% confidence level. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved

    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

    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

    Observation of the decay B-s(0) -> (D)over-bar(0)phi

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    First observation of the decay B-s(0) -> (D) over bar (0)phi is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The significance of the signal is 6.5 standard deviations. The branching fraction is measured relative to that of the decay B-S(0) -> (D) over bar (0)phi to be beta B-S(0) -> (D) over bar (0)phi/beta B-S(0) -> (D) over bar (0)(K) over bar*(0) = 0.069 +/- 0.013 (stat) +/- 0.007 (syst). The first measurement of the ratio of branching fractions for the decays beta B-S(0) -> (D) over bar (0)(K) over bar*(0) and beta B-S(0) -> (D) over bar (0)(K) over bar*(0) is found to be beta B-S(0) -> (D) over bar (0)(K) over bar*(0/)beta B-S(0) -> (D) over bar (0)(K) over bar*(0=7.8) +/- 0.7(stat) +/- 0.3 (syst) +/- 0.6 (f(s)/f(d)) where the last uncertainty is due to the ratio of the B(s)(0)and B-0 fragmentation fractions

    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
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