5 research outputs found

    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

    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

    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

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

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    A search for the rare decay D-0 -> mu(+) mu(-) is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb(-1), of pp collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of B(D-0 -> mu(+) mu(-)) < 6.2 (7.6) x 10(-9) at 90% (95%) confidence level. This result represents an improvement of more than a factor twenty with respect to previous 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
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