335 research outputs found

    Quality Control of Mass-Produced GEM Detectors for the CMS GE1/1 Muon Upgrade

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    The series of upgrades to the Large Hadron Collider, culminating in the High Luminosity Large Hadron Collider, will enable a significant expansion of the physics program of the CMS experiment. However, the accelerator upgrades will also make the experimental conditions more challenging, with implications for detector operations, triggering, and data analysis. The luminosity of the proton-proton collisions is expected to exceed 2‚ąí3√ó10342-3\times10^{34}~cm‚ąí2^{-2}s‚ąí1^{-1} for Run 3 (starting in 2022), and it will be at least 5√ó10345\times10^{34}~cm‚ąí2^{-2}s‚ąí1^{-1} when the High Luminosity Large Hadron Collider is completed for Run 4. These conditions will affect muon triggering, identification, and measurement, which are critical capabilities of the experiment. To address these challenges, additional muon detectors are being installed in the CMS endcaps, based on Gas Electron Multiplier technology. For this purpose, 161 large triple-Gas Electron Multiplier detectors have been constructed and tested. Installation of these devices began in 2019 with the GE1/1 station and will be followed by two additional stations, GE2/1 and ME0, to be installed in 2023 and 2026, respectively. The assembly and quality control of the GE1/1 detectors were distributed across several production sites around the world. We motivate and discuss the quality control procedures that were developed to standardize the performance of the detectors, and we present the final results of the production. Out of 161 detectors produced, 156 detectors passed all tests, and 144 detectors are now installed in the CMS experiment. The various visual inspections, gas tightness tests, intrinsic noise rate characterizations, and effective gas gain and response uniformity tests allowed the project to achieve this high success rate

    Production and validation of industrially produced large-sized GEM foils for the Phase-2 upgrade of the CMS muon spectrometer

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    The upgrade of the CMS detector for the high luminosity LHC (HL-LHC) will include gas electron multiplier (GEM) detectors in the end-cap muon spectrometer. Due to the limited supply of large area GEM detectors, the Korean CMS (KCMS) collaboration had formed a consortium with Mecaro Co., Ltd. to serve as a supplier of GEM foils with area of approximately 0.6 m2^{2}. The consortium has developed a double-mask etching technique for production of these large-sized GEM foils. This article describes the production, quality control, and quality assessment (QA/QC) procedures and the mass production status for the GEM foils. Validation procedures indicate that the structure of the Korean foils are in the designed range. Detectors employing the Korean foils satisfy the requirements of the HL-LHC in terms of the effective gain, response uniformity, rate capability, discharge probability, and hardness against discharges. No aging phenomena were observed with a charge collection of 82 mC/cm2^{2}. Mass production of KCMS GEM foils is currently in progress

    Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at s \sqrt{s} = 13 TeV

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    International audienceMeasurements of the inclusive and normalised differential cross sections are presented for the production of single top quarks in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data used were recorded with the CMS detector at the LHC during 2016‚Äď2018, and correspond to an integrated luminosity of 138 fb‚ąí1^{‚ąí1}. Events containing one electron and one muon in the final state are analysed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events is used to separate the signal from the dominant tt‚Äĺ \textrm{t}\overline{\textrm{t}} background. A cross section of 79.2¬Ī0.9(stat)‚ąí8.0+7.7(syst)¬Ī1.2(lumi) 79.2\pm 0.9{\left(\textrm{stat}\right)}_{-8.0}^{+7.7}\left(\textrm{syst}\right)\pm 1.2\left(\textrm{lumi}\right) pb is obtained, consistent with the predictions of the standard model. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requirement of exactly one jet coming from the fragmentation of a bottom quark. The resulting distributions are unfolded to particle level and agree with the predictions at next-to-leading order in perturbative quantum chromodynamics.[graphic not available: see fulltext

    Search for nonresonant Higgs boson pair production in final state with two bottom quarks and two tau leptons in proton-proton collisions at <math altimg="si1.svg"><msqrt><mrow><mi>s</mi></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>13</mn><mtext> TeV</mtext></math>