Publications by authors named "Petridis K"

The lifetime of the [Formula: see text] meson is measured using semileptonic decays having a [Formula: see text] meson and a muon in the final state. The data, corresponding to an integrated luminosity of [Formula: see text], are collected by the LHCb detector in [Formula: see text] collisions at a centre-of-mass energy of 8 TeV. The measured lifetime is [Formula: see text]where the first uncertainty is statistical and the second is systematic.

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  • - The mass of the top quark is determined using data from candidate events featuring at least six jets, collected by the CMS detector during proton-proton collisions at [Formula: see text] TeV in 2011, totaling an integrated luminosity of 3.54 [Formula: see text].
  • - Each event undergoes a kinematic fit of the jets to a [Formula: see text] hypothesis to accurately reconstruct the mass.
  • - The final measurement for the top-quark mass is reported as [Formula: see text] GeV, which is further refined by combining it with earlier measurements from different decay modes by CMS, resulting in a combined mass of [Formula: see text] GeV.
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  • The CMS experiment conducted a search for heavy right-handed neutrinos and right-handed [Formula: see text] bosons, which are part of theoretical extensions of the standard model of particle physics.
  • This search utilized data from proton-proton collisions at 8[Formula: see text] with an integrated luminosity of 19.7 [Formula: see text], focusing on two lepton plus two jet events.
  • The findings showed that the excluded mass region for these particles at a 95% confidence level is significantly larger than previous studies, especially in the range of neutrino masses below the [Formula: see text] boson mass.
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  • * A data-driven isolation template method was employed to accurately determine the prompt diphoton yield, specifically focusing on photons with transverse energies above certain thresholds.
  • * The results, including cross sections as a function of various parameters, are compared against theoretical predictions from quantum chromodynamics (QCD) at different order levels to assess their alignment with experimental data.
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  • - The study reports on the diphoton decay mode of the Higgs boson, utilizing data from the CMS experiment gathered during the 2011 and 2012 LHC proton-proton collisions, with a total integrated luminosity of 24.8 fb⁻¹.
  • - A significant signal for the Higgs boson is detected at a mass close to 125 GeV, aligning with standard model predictions, and the mass is precisely measured along with its signal strength.
  • - The research also includes measurements of signal strength variations linked to various production methods and performs hypothesis testing to differentiate between spin-0 and spin-2 models of particle physics.
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A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at √s=8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 fb(-1) collected by the CMS experiment at the LHC in 2012.

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Article Synopsis
  • - The study examines unusual production of top quark-antiquark pairs from proton-proton collisions at a high energy level (√s=8 TeV), utilizing data from the CMS detector at the LHC.
  • - A total of 19.7 fb(-1) of data was analyzed, and the results show that the observed mass spectrum aligns with predictions made by the standard model of particle physics.
  • - For the first time, limitations on production cross sections and branching fractions are set, exploring specific new physics models that have not been addressed by previous precise measurements.
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We present a measurement of form-factor-independent angular observables in the decay B(0)→K*(892)(0)μ(+)μ(-). The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV.

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The result of a search for the decay B(c)(+) → B(s)(0) π+ is presented, using the B(s)(0) → D(s)(-)π+ and B(s)(0) → J/ψ Ø channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1 fb(-1) taken at a center-of-mass energy of 7 TeV, and 2 fb(-1) taken at 8 TeV. The decay B(c)(+) → B(s)(0)π+ is observed with significance in excess of 5 standard deviations independently in both decay channels.

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A measurement of the CP asymmetry in B(+)→K(+)μ(+)μ(-) decays is presented using pp collision data, corresponding to an integrated luminosity of 1.0 fb(-1), recorded by the LHCb experiment during 2011 at a center-of-mass energy of 7 TeV. The measurement is performed in seven bins of μ(+)μ(-) invariant mass squared in the range 0.

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A search for the lepton-flavor-violating decays B(s)0→e(±)μ(∓) and B0→e(±)μ(∓) is performed with a data sample, corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions at √s=7 TeV, collected by the LHCb experiment. The observed number of B(s)0→e(±)μ(∓) and B0→e(±)μ(∓) candidates is consistent with background expectations.

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A broad peaking structure is observed in the dimuon spectrum of B+ → K+ μ+ μ- decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the B+ → K+ μ+ μ- decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be 4191(-8)(+9)  MeV/c2 and 65(-16)(+22)  MeV/c2, respectively, where the uncertainties include statistical and systematic contributions.

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An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb(-1) of integrated luminosity.

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The quantum numbers of the X(3872) meson are determined to be J(PC)=1(++) based on angular correlations in B(+)→X(3872)K(+) decays, where X(3872)→π(+)π(-)J/ψ and J/ψ→μ(+)μ(-). The data correspond to 1.0 fb(-1) of pp collisions collected by the LHCb detector.

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Using pp collision data corresponding to an integrated luminosity of 1.0 fb(-1) and collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in B(s)(0)→K(-)π(+) decays, A(CP)(B(s)(0)→K(-)π(+)=0.27±0.

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A first flavor-tagged measurement of the time-dependent CP-violating asymmetry in B(s)(0) → ϕϕ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between B(s)(0)-B(s)(0) mixing and the b → sss gluonic penguin decay amplitude. Using a sample of pp collision data corresponding to an integrated luminosity of 1.

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We present a measurement of the direct CP-violating charge asymmetry in B(±) mesons decaying to J/ψK(±) and J/ψπ(±) where J/ψ decays to μ(+) μ(-), using the full run II data set of 10.4 fb(-1) of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. A difference in the yield of B(-) and B(+) mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of A(J/ψK) = [0.

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A search for the decays B(0)((s))→μ(+)μ(-)μ(+)μ(-) and B(0)→μ(+)μ(-)μ(+)μ(-) is performed using data, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector in 2011. The number of candidates observed is consistent with the expected background and, assuming phase-space models of the decays, limits on the branching fractions are set: B(B(s)(0)→μ(+)μ(-)μ(+)μ(-))<1.

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Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0 fb(-1) of data collected in 2011 with the LHCb detector. Significant Λ(b)(0) → J/ψΛ, Ξ(b((-) → J/ψΞ(-) and Ω(b)(-) → J/ψΩ(-) signals are observed and the corresponding masses are measured to be M(Λ(b)(0))=5619.

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Article Synopsis
  • The study reports the first measurements of vector-boson production associated with a top quark-antiquark pair during proton-proton collisions at a center-of-mass energy of 7 TeV, using data from the CMS detector at the LHC from 2011.
  • Two analysis channels were employed: a trilepton analysis for ttZ events and a same-sign dilepton analysis for ttV events (where V can be W or Z).
  • The measured cross sections are σ(ttZ) = 0.28 pb and σ(ttV) = 0.43 pb, both significant at over 3 standard deviations, and they align with theoretical predictions within the stated uncertainties.
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The properties of the orbitally excited (L=1) Bs(0) states are studied by using 1.0  fb(-1) of pp collisions at sqrt[s]=7  TeV collected with the LHCb detector. The first observation of the Bs2*(5840)(0) meson decaying to B*+ K- is reported, and the corresponding branching fraction measured relative to the B+ K- decay mode.

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A search for the pair production of a heavy, narrow resonance decaying into two jets has been performed using events collected in sqrt[s] = 7 TeV pp collisions with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 5.0 fb(-1).

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We report a measurement of the time-dependent ratio of D(0) → K(+) π- to D(0) → K(-) π(+) decay rates in D(*+)-tagged events using 1.0 fb(-1) of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x('2) = (-0.

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A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 fb(-1), collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used.

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The polarizations of the Υ(1S), Υ(2S), and Υ(3S) mesons are measured in proton-proton collisions at sqrt[s] = 7 TeV, using a data sample of Υ(nS) → μ +μ- decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb(-1). The dimuon decay angular distributions are analyzed in three different polarization frames.

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