2,422 research outputs found

    A study of B0-anti-B0 oscillations with full reconstructed B mesons with the BABAR detector

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    Time-dependent B0-anti-B0 flavor oscillations are studied in e+e- annihilation data collected with the BABAR detector at center-of-mass energies near the Upsilon(4S) resonance. We report a preliminary result for the time-dependent B0-anti-B0 oscillation frequency, Delta_md = 0.512 +/- 0.017 +/- 0.022 hbar ps^{-1}.Comment: 4 pages, 2 postscript figues, submitted to DPF200

    Exotic Searches at LHC and Tevatron

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    Successful operation of the Large Hadron Collider has led to more than 1 fb^-1 of data recorded with both ATLAS and CMS detectors by summer of 2011. This large amount of data has allowed to perform numerous searches for rare processes beyond the Standard Model, many of which are competitive with previous searches performed with the CDF and D0 detectors at the Tevatron. In this talk the most recent searches at the hadron colliders are reviewed.Comment: Proceedings for XXXI PHYSICS IN COLLISION, Vancouver, BC Canada, August 28 - September 1, 201

    High Voltage System for the CMS Electromagnetic Calorimeter

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    The CMS electromagnetic calorimeter (ECAL) is made of about 75000 lead tungstate crystals. The 61200 crystals of the barrel part are read by avalanche photodiodes (APD) with internal amplification of the signal. Since the gain strongly depends on the bias voltage, the APDs require a very stable power supply system. To preserve the high energy resolution of the calorimeter, a stability of the bias voltage of the order of 10^-4 is required over several months, a typical interval between absolute calibrations of the full read-out chain with physics events. This paper describes the High Voltage power supply system developed for CMS ECAL and its performances as measured in laboratory tests and during test-beam operations of several modules of the calorimeter

    Intercalibration of the barrel electromagnetic calorimeter of the CMS experiment at start-up

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    Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated

    Determining Higgs couplings with a model-independent analysis of h ->gamma gamma

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    Discovering a Higgs boson at the LHC will address a major outstanding issue in particle physics but will also raise many new questions. A concerted effort to determine the couplings of this new state to other Standard Model fields will be of critical importance. Precise knowledge of these couplings can serve as a powerful probe of new physics, and will be needed in attempts to accommodate such a new boson within specific models. In this paper, we present a method for constraining these couplings in a model-independent way, focusing primarily on an exclusive analysis of the gamma gamma final state. We demonstrate the discriminating power of fully exclusive analyses, and discuss ways in which information can be shared between experimentalists and theorists in order to facilitate collaboration in the task of establishing the true origins of any new physics discovered at the LHC.Comment: 24 pages, 4 figure

    Energy Resolution Performance of the CMS Electromagnetic Calorimeter

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    The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals

    Search for massive resonances decaying in to WW,WZ or ZZ bosons in proton-proton collisions at root s=13 TeV

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