320 research outputs found

    Search for High-Mass Resonances in the Dilepton Final State with the CMS Detector

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    A search for narrow resonances at high mass in the dimuon and dielectron channels has been performed by the CMS experiment at the CERN LHC, using pp collision data recorded at sqrt{s}=7 TeV. The event samples correspond to an integrated luminosity of 1.1 fb^{-1}. Heavy dilepton resonances are predicted in theoretical models with extra gauge bosons (Z') or as Kaluza-Klein graviton excitations (G_{KK}) in the Randall-Sundrum model. Upper limits on the inclusive cross section of Z'(G_{KK}) to l+l- relative to Z to l+l- are presented. These limits exclude at 95 % confidence level a Z' with standard-model-like couplings below 1940 GeV, the superstring-inspired Z_{psi} below 1620 GeV, and, for values of the coupling parameter k/M_{Pl} of 0.05 (0.1), Kaluza--Klein gravitons below 1450 (1780)GeV.Comment: 3 pages, 5 figures, XXXI Physics In Collision 2011 Proceeding

    Database usage for the CMS ECAL Laser Monitoring System

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    The CMS detector at LHC is equipped with a high precision electromagnetic crystal calorimeter (ECAL). The crystals experience a transparency change when exposed to radiation during LHC operation, which recovers in absents of irradiation on the time scale of hours. This change of the crystal response is monitored with a laser system which performs a transparency measurement of each crystal of the ECAL within twenty minutes. The monitoring data is analyzed on a PC farm attached to the central data acquisition system of CMS. After analyzing the raw data, a reduced data set is stored in the Online Master Data Base (OMDS) which is connected to the online computing infrastructure of CMS. The data stored in OMDS, representing the largest data set stored in OMDS for ECAL, contains all necessary information to perform a detailed crystal response monitoring as well as an analysis of the dynamics of the transparency change. For the CMS physics event data reconstruction, only a reduced set of information from the transparency measurement is required. This data is stored in the offline Reconstruction Conditions data base (ORCOF). To transfer the data from the OMDS to ORCOF, the reduced data is transferred to Off-line Reconstruction Conditions DB On-line subset (ORCON) in a procedure known as Online to Offline transfer, which includes various checks for data consistency. In this talk we describe the laser monitoring work flow and the specifics of the data bases usage for the ECAL laser monitoring system. The strategies implemented to optimize the data transfer and to perform quality checks are being presented

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

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