38 research outputs found

    Observation of Bell Inequality violation in B mesons

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    A pair of B0Bˉ0B^0\bar B^0 mesons from Υ(4S)\Upsilon(4S) decay exhibit EPR type non-local particle-antiparticle (flavor) correlation. It is possible to write down Bell Inequality (in the CHSH form: S≤2S\le2) to test the non-locality assumption of EPR. Using semileptonic B0B^0 decays of Υ(4S)\Upsilon(4S) at Belle experiment, a clear violation of Bell Inequality in particle-antiparticle correlation is observed: S=2.725+-0.167(stat)+-0.092(syst)Comment: Conference Proceeding for Garda Lake Workshop 2003 "Mysteries, Puzzles and Paradoxes in Quantum Mechanics

    Performance of CMS ECAL Preshower in 2007 test beam

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    The Preshower detector is part of the CMS Electromagnetic Calorimeter, located in the endcap regions, in front of the lead tungstate crystals. It consist of two orthogonal planes of silicon strip sensors interleaved with two planes of lead absorbers. A combined beam test of close-to-final prototypes of the Hadron calorimeter, the crystal calorimeter and the Preshower detector was performed in the summer of 2007. Calibrations were made using electron and pion data. The combined crystal and Preshower energy resolution was studied using electrons. Good signal/noise performance was obtained in both sets of measurement

    Detector Control System for the Electromagnetic Calorimeter of the CMS experiment

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    The Compact Muon Solenoid (CMS) is one of the general purpose particle detectors at the Large Hadron Collider (LHC) at CERN. The challenging constraints on the design of one of its sub-detectors, the Electromagnetic Calorimeter (ECAL), required the development of a complex Detector Control System (DCS). In this paper the general features of the CMS ECAL DCS during the period of commissioning and cosmic running will be presented. The feedback from the people involved was used for several upgrades of the system in order to achieve a robust, flexible and stable control system. A description of the newly implemented features for the CMS ECAL DCS subsystems will be given as well

    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

    RICH detectors for the LHCb experiment

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    Performance of Si sensors irradiated 5x1014 n/cm2

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    The expected particle fluence in the inner part of the CMS Preshower is calculated to be 1.6x1014 cm^-2 for neutrons and 0.4x1014 cm2 for charged hadrons. Since the error of the calculation is high and/or unexpected accidental beam miss-alignments might happen we have irradiated Preshower silicon sensors to fluences up to 5x1014 n/cm2 to verify that they hold voltages necessary to reach the full charge collection efficiency. All irradiated sensors showed no signs of breakdown up to 1000 V, the maximum voltage applied. For all but one the operating voltage was lower than 900 V and a charge collection efficiency plateau was at least 200 V long. No noisy channels were observed at the extreme voltages. The measured charge was 71+-12% and 59+-12% for sensors irradiated to 3x1014 n/cm2 and 5x1014 n/cm2, respectively. These values are consistent with the extrapolation from previous measurements made on sensors irradiated to 2.3x1014 n/cm2. The work presents the results of static and dynamic measurements and shows that our design and the technology are very robust

    Noise measurement on Preshower Si sensors

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    Throughout the past couple of years when we were designing the Preshower silicon sensors we have noticed that some of them have strips with a noise higher than the average and not correlated to the leakage current. In order to investigate this effect we have developed a set-up for noise measurement on wafers and diced sensors that does not require bonding. The set-up is based on the DeltaStream chip coupled to a probe card with 32 pins at a pitch of 1.9 mm. All the digital electronics, including the analogue-to-digital converter and a microprocessor, is placed on a motherboard which communicates with a PC via an RS232 line. We have tested 45 sensors and found that some strips which have an above average noise, also have a higher relative current increase as a function of voltage, deltaI/(I deltaV), even though their leakage current is below 50 nA. We also observed that on these strips th e breakdown occurs within about 60 V from the onset of the noise. The source of this noise is not yet clear and the investigation is going on