1,690 research outputs found

    Web-based monitoring tools for Resistive Plate Chambers in the CMS experiment at CERN

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    The Resistive Plate Chambers (RPC) are used in the CMS experiment at the trigger level and also in the standard offline muon reconstruction. In order to guarantee the quality of the data collected and to monitor online the detector performance, a set of tools has been developed in CMS which is heavily used in the RPC system. The Web-based monitoring (WBM) is a set of java servlets that allows users to check the performance of the hardware during data taking, providing distributions and history plots of all the parameters. The functionalities of the RPC WBM monitoring tools are presented along with studies of the detector performance as a function of growing luminosity and environmental conditions that are tracked over time

    Radiation background with the CMS RPCs at the LHC

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    The Resistive Plate Chambers (RPCs) are employed in the CMS Experiment at the LHC as dedicated trigger system both in the barrel and in the endcap. This article presents results of the radiation background measurements performed with the 2011 and 2012 proton-proton collision data collected by CMS. Emphasis is given to the measurements of the background distribution inside the RPCs. The expected background rates during the future running of the LHC are estimated both from extrapolated measurements and from simulation

    Impact of magnetic field on the stability of the CMS GE1/1 GEM detector operation

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    The Gas Electron Multiplier (GEM) detectors of the GE1/1 station of the CMS experiment have been operated in the CMS magnetic field for the first time on the 7th^{th} of October 2021. During the magnetic field ramps, several discharge phenomena were observed, leading to instability in the GEM High Voltage (HV) power system. In order to reproduce the behavior, it was decided to conduct a dedicated test at the CERN North Area with the Goliath magnet, using four GE1/1 spare chambers. The test consisted in studying the characteristics of discharge events that occurred in different detector configurations and external conditions. Multiple magnetic field ramps were performed in sequence: patterns in the evolution of the discharge rates were observed with these data. The goal of this test is the understanding of the experimental conditions inducing discharges and short circuits in a GEM foil. The results of this test lead to the development of procedure for the optimal operation and performance of GEM detectors in the CMS experiment during the magnet ramps. Another important result is the estimation of the probability of short circuit generation, at 68 % confidence level, pshort_{short}HV^{HV} OFF^{OFF} = 0.42−0.35+0.94^{-0.35+0.94}% with detector HV OFF and pshort_{short}HV^{HV} OFF^{OFF} < 0.49% with the HV ON. These numbers are specific for the detectors used during this test, but they provide a first quantitative indication on the phenomenon, and a point of comparison for future studies adopting the same procedure

    Search for heavy Majorana neutrinos in e+-e+-+ jets and e+-ÎŒ+-+ jets events in proton-proton collisions at s = 8 s√=8 TeV

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    A search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 fb−1 of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015–0.72 for |VeN|2 and 6.6 × 10−5−0.47 for |VeNVÎŒN∗|2/(|VeN|2 + |VÎŒN|2), where VℓN is the mixing element describing the mixing of the heavy neutrino with the SM neutrino of flavour ℓ. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 200 GeV

    CMS RPC muon detector performance with 2010-2012 LHC data

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    The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the Large Hadron Collider (LHC) is equipped with a redundant system made of Resistive Plate Chambers (RPCs) and Drift Tube (DT) chambers in the barrel, RPC and Cathode Strip Chambers (CSCs) in the endcap region. In this paper, the operations and the performance of the RPC system during the first three years of LHC activity are presented. The stability of the RPC performance, in terms of efficiency, cluster size and noise, is also reported. Finally, the radiation background levels on the RPC system have been measured as a function of the LHC luminosity. Extrapolations to the High Luminosity LHC conditions are also discussed

    Multiplicity and rapidity dependence of strange hadron production in pp, pPb, and PbPb collisions at the LHC

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    Measurement of differential cross sections for top quark pair production using the lepton plus jets final state in proton-proton collisions at 13 TeV