29 research outputs found

    Measurement of |V(cs)| using W decays at LEP-2

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    Decays of W± bosons, produced at LEP2, have been used to measure the0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Measurements of ψ(2S)\psi(2S) and X(3872)J/ψπ+πX(3872) \to J/\psi\pi^+\pi^- production in pppp collisions at s=8\sqrt{s} = 8 TeV with the ATLAS detector

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    See paper for full list of authors - 42 pages in total, author list starting page 26, 10 figures, 8 tables. Submitted to JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2015-03/International audienceDifferential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872)X(3872) and ψ(2S)\psi(2S), in the decay mode J/ψπ+πJ/\psi \pi^+\pi^-, measured using 11.4 fb1^{-1} of pppp collisions at s=8\sqrt{s} = 8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S)X(3872)/\psi(2S) is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of X(3872)X(3872) and ψ(2S)\psi(2S). Assuming independent single effective lifetimes for non-prompt X(3872)X(3872) and ψ(2S)\psi(2S) production gives RB=B(BX(3872) + any)B(X(3872J/ψπ+π)B(Bψ(2S) + any)B(ψ(2S)J/ψπ+π)=(3.95±0.32(stat)±0.08(sys))×102R_B = \frac{\mathcal{B}(B \rightarrow X(3872)\textrm{ + any}) \mathcal{B}(X(3872 \rightarrow J/\psi\pi^+\pi^-)}{\mathcal{B}(B \rightarrow \psi(2S)\textrm{ + any}) \mathcal{B}(\psi(2S) \rightarrow J/\psi\pi^+\pi^-)} = (3.95 \pm 0.32 \mathrm{(stat)} \pm 0.08\mathrm{(sys)}) \times 10^{-2}, while separating short- and long-lived contributions, assuming that the short-lived component is due to BcB_c decays, gives RB=(3.57±0.33(stat)±0.11(sys))×102R_B = (3.57 \pm 0.33\mathrm{(stat)} \pm 0.11\mathrm{(sys)}) \times 10^{-2}, with the fraction of non-prompt X(3872)X(3872) produced via BcB_c decays for pT(X(3872))>10p_\mathrm{T}(X(3872)) > 10 GeV being (25±13(stat)±2(sys)±5(spin))%(25 \pm 13\mathrm{(stat)} \pm 2\mathrm{(sys)} \pm 5\mathrm{(spin)})\%. The distributions of the dipion invariant mass in the X(3872)X(3872) and ψ(2S)\psi(2S) decays are also measured and compared to theoretical predictions

    Search for excited electrons and muons in √s=8 TeV proton–proton collisions with the ATLAS detector

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    The ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp → ℓℓ* → ℓℓγ, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb[superscript −1] of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m[subscript ℓ*]. For m[subscript ℓ*] ≥ 0.8 TeV, the respective upper limits on σB(ℓ* → ℓγ) are 0.75 and 0.90 fb for the e* and μ* searches. Limits on σB are converted into lower bounds on the compositeness scale Λ. In the special case where Λ = m[subscript ℓ*], excited-electron and excited-muon masses below 2.2 TeV are excluded.United States. Dept. of EnergyNational Science Foundation (U.S.)Brookhaven National Laborator

    Searches for neutral Higgs bosons in e+ e- collisions around s**(1/2) = 189-GeV

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    0info:eu-repo/semantics/publishe

    Cross-sections and leptonic forward backward asymmetries from the Z0 running of LEP

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    info:eu-repo/semantics/publishe

    Measurement of the B0(s) lifetime and study of B0(s) - anti-B0(s) oscillations using D(s)l events

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    Lifetime and oscillations of B-s(0) mesons have been studied in events with a large transverse momentum lepton and a D-s of opposite electric charge in the same hemisphere, selected from about 3.6 million hadronic Z(0) decays accumulated by DELPHI between 1992 and 1995. The B-s(0) lifetime and the fractional width difference between the two physical B-s(0) states have been found to be: tau(Bs0) = (1.42(-0.13)(+0.14)(stat.) +/- 0.03(syst)) ps Delta Gamma(Bs0) /Gamma(Bs0) lt 0.46 at the 95% C.L. In the latter result it has been assumed that tau(Bs0) = tau(Bd0). Using the same sample, a limit on the mass difference between the physical B-s(0) states has been set: Delta m(Bs0) gt 7.4 ps(-1) at the 95% C.L. with a corresponding sensitivity equal to 8.1 ps(-1)

    Search for scalar fermions and longlived scalar leptons at center-of-mass energies of 130-GeV to 172-GeV

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    Data taken by DELPHI during the 1995 and 1996 LEP runs have been used to search for the supersymmetric partners of electron, muon and tau leptons and of top and bottom quarks. The observations are in agreement with standard model predictions. Limits are set on sfermion masses. Searches for long lived scalar leptons from low scale supersymmetry breaking models exclude stau masses below 55 GeV/c2 at the 95% confidence level irrespective of the gravitino mass

    FIRST EVIDENCE OF HARD SCATTERING PROCESSES IN SINGLE TAGGED GAMMA-GAMMA-COLLISIONS

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    For the first time, multihadronic production from single tagged gamma gamma collisions has been studied, where one of the scattered leptons was tagged at very low virtual photon absolute mass squared ([Q(2)] = 0.06 (GeV/c(2))(2)). Data collected during 1991 and 1992 in the DELPHI experiment at LEP are shown to agree well with predictions which included the non-perturbative vector meson dominance model in which the interacting photons are assumed to have converted into a vector meson (rho, omega or pi), a quark-parton model which describes direct photon interactions and a QCD-based model which considers the photon to have quark and gluon structure functions. Five different parametrizations of these structure functions were used and the predictions compared with the data. This study confirms recent results from no-tag experiments in requiring a QCD-based component to successfully describe the data, indicating that the photon has a significant partonic content

    FIRST EVIDENCE OF HARD SCATTERING PROCESSES IN SINGLE TAGGED GAMMA-GAMMA-COLLISIONS

    No full text
    For the first time, multihadronic production from single tagged γγ collisions has been studied, where one of the scattered leptons was tagged at very low virtual photon absolute mass squared (〈Q2〉 = 0.06 (GeV/c2)2). Data collected during 1991 and 1992 in the DELPHI experiment at LEP are shown to agree well with predictions which included the non-perturbative vector meson dominance model in which the interacting photons are assumed to have converted into a vector meson (ρ{variant}, ω or π), a quark-parton model which describes direct photon interactions and a QCD-based model which considers the photon to have quark and gluon structure functions. Five different parametrizations of these structure functions were used and the predictions compared with the data. This study confirms recent results from no-tag experiments in requiring a QCD-based component to successfully describe the data, indicating that the photon has a significant partonic content. © 1995

    Search for composite and exotic fermions at LEP-2

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    A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48~pb1^{-1} at an e+ee^+e^- centre-of-mass energy of 183~GeV and about 20~pb1^{-1} equally shared between the centre-of-mass energies of 172~GeV and 161~GeV. The search for pair-produced new leptons establishes 95\% confidence level mass limits in the region between 70~GeV/c2c^2 and 90~GeV/c2c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermionA search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio
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