167 research outputs found

    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

    Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThe results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (pTmissp_\text{T}^\text{miss}), are reported. The study is based on a sample of proton-proton collisions at s\sqrt{s} =13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb‚ąí1^{-1}. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low pTmissp_\text{T}^\text{miss} regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level

    Search for narrow trijet resonances in proton-proton collisions at s\sqrt{s} = 13 TeV