38 research outputs found

    Search for long-lived particles decaying to leptons with large impact parameter in proton-proton collisions at root s=13 TeV

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    A search for new long-lived particles decaying to leptons using proton–proton collision data produced by the CERN LHC at s√=13TeV is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10cm and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113)fb−1 in the ee channel (eμ and μμ channels). The search is designed to be sensitive to a wide range of models with displaced eμ, ee, and μμ final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date

    Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

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    Contains fulltext : 121524.pdf (preprint version ) (Open Access

    Search for Charged Higgs bosons: Combined Results Using LEP Data

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    The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments are statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant excess has been observed when compared to the Standard Model background prediction, and the combined LEP data exclude large regions of the model parameter space. Charged Higgs bosons with mass below 80 GeV/c^2 (Type II scenario) or 72.5 GeV/c^2 (Type I scenario, for pseudo-scalar masses above 12 GeV/c^2) are excluded at the 95% confidence level

    First measurement of time-dependent CP violation in Bs0K+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

    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

    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

    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
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