2,431 research outputs found
Data compression for the first G-APD Cherenkov Telescope
No full textAbstract not availableM.L. Ahnen, M. Balbo, M. Bergmann, A. Biland, T. Bretz, J. Buß, D. Dorner, S. Einecke, J. Freiwald, C. Hempfling, D. Hildebrand, G. Hughes, W. Lustermann, E. Lyard, K. Mannheim, K. Meier, S. Mueller, D. Neise, A. Neronov, A.-K. Overkemping, A. Paravac, F. Pauss, W. Rhode, T. Steinbring, F. Temme, J. Thaele, S. Toscano, P. Vogler, R. Walter, A. Wilber
Measurement of associated W+ charm production in pp collisions at √s=7 TeV
No full textOpen Access, Copyright CERN, for the benefit of the CMS Collaboration.Measurements are presented of the associated production of a W boson and a charm-quark jet (W + c) in pp collisions at a center-of-mass energy of 7 TeV. The analysis is conducted with a data sample corresponding to a total integrated luminosity of 5 fb−1, collected by the CMS detector at the LHC. W boson candidates are identified by their decay into a charged lepton (muon or electron) and a neutrino. The W + c measurements are performed for charm-quark jets in the kinematic region p jet T > 25 GeV, |ηjet| 25 GeV) and σ(pp → W + c + X)× B (W → ℓν) = 84.1 ± 2.0 (stat.) ± 4.9 (syst.) pb ( p ℓ T > 35 GeV), and the cross section ratios σ(pp → W+ + c ¯ + X)/σ(pp → W− + c + X) = 0.954 ± 0.025 (stat.) ± 0.004 (syst.) ( p ℓ T > 25 GeV) and σ(pp → W+ + c ¯ + X)/σ(pp → W− + c + X) = 0.938 ± 0.019 (stat.) ± 0.006 (syst.) ( p ℓ T > 35 GeV). Cross sections and cross section ratios are also measured differentially with respect to the absolute value of the pseudorapidity of the lepton from the W-boson decay. These are the first measurements from the LHC directly sensitive to the strange quark and antiquark content of the proton. Results are compared with theoretical predictions and are consistent with the predictions based on global fits of parton distribution functions
Wavelength shifter strips and G-APD arrays for the read-out of the z-coordinate in axial PET modules
No full textThe CMS crystal calorimeter
No full textThe measurement of the energy of electrons and photons with very high accuracy is of primary importance far the study of many physics processes at the Large Hadron Collider (LHC), in particular for the search of the Higgs Boson. The CMS experiment will use a crystal calorimeter with pointing geometry, almost covering 4p, as it offers a very good energy resolution. It is divided into a barrel composed of 61200 lead tungstate crystals, two end-caps with 14648 crystals and a pre-shower detector in front of the end-cap. The challenges of the calorimeter design arise from the high radiation environment, the 4 Tesla magnetic eld, the high bunch crossing rate of 40 MHz and the large dynamic range, requiring the development of fast, radiation hard crystals, photo-detectors and readout electronics. An overview of the construction and design of the calorimeter will be presented, with emphasis on some of the details required to meet the demanding performance goals. 19 Refs
Search for a Heavy Gauge Boson W′ in the Final State With an Electron and Large Missing Transverse Energy in Pp Collisions at S=7 Tev
No full textA search for a heavy gauge boson W′ has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse energy imbalance ET miss, using proton–proton collision data corresponding to an integrated luminosity of 36 pb−1. No excess above standard model expectations is seen in the transverse mass distribution of the electron-ET miss system. Assuming standard-model-like couplings and decay branching fractions, a W′ boson with a mass less than 1.36 TeV/c2 is excluded at 95% confidence level. © 2011 CER
Calibration and performance of the photon sensor response of FACT - the first G-APD Cherenkov telescope
No full textThe First G-APD Cherenkov Telescope (FACT) is the first in-operation test of the performance of silicon photo detectors in Cherenkov Astronomy. For more than two years it is operated on La Palma, Canary Islands (Spain), for the purpose of long-term monitoring of astrophysical sources. For this, the performance of the photo detectors is crucial and therefore has been studied in great detail. Special care has been taken for their temperature and voltage dependence implementing a correction method to keep their properties stable. Several measurements have been carried out to monitor the performance. The measurements and their results are shown, demonstrating the stability of the gain below the percent level. The resulting stability of the whole system is discussed, nicely demonstrating that silicon photo detectors are perfectly suited for the usage in Cherenkov telescopes, especially for long-term monitoring purpose.A. Biland, T. Bretz, J. Buß, V. Commichau, L. Djambazov, D. Dorner, S. Einecke, D. Eisenacher, J. Freiwald, O. Grimm, H. von Gunten, C. Haller, C. Hempfling, D. Hildebrand, G. Hughes, U. Horisberger, M.L. Knoetig, T. Krähenbühl, W. Lustermann, E. Lyard, K. Mannheim, K. Meier, S. Mueller, D. Neise, A.-K. Overkemping, A. Paravac, F. Pauss, W. Rhode, U. Röser, J.-P. Stucki, T. Steinbring, F. Temme, J. Thaele, P. Vogler, R. Walter and Q. Weitze
Study of the Process and Limits on Anomalous Quartic Gauge Boson Couplings at LEP
No full textThe process e+e- --> W+ W- \gamma is studied using the data collected by the L3 detector at LEP. New results, corresponding to an integrated luminosity of 427.4 pb-1 at centre-of-mass energies from 192~GeV to 207~GeV, are presented. The W+W-\gamma cross sections are measured to be in agreement with Standard Model expectations. No hints of anomalous quartic gauge boson couplings are observed. Limits at 95\% confidence level are derived using also the process e+e- --> \nu\bar\nu\gamma\gamma.The process e + e − →W + W − γ is studied using the data collected by the L3 detector at LEP. New results, corresponding to an integrated luminosity of 427.4 pb −1 at centre-of-mass energies from 192 to 207 GeV, are presented.
The W + W − γ cross sections are measured to be in agreement with Standard Model expectations. No hints of anomalous quartic gauge boson couplings are observed. Limits at 95% confidence level are derived using also the process e + e − →ν ν ̄ γγ .The process e+e- -> W+ W- gamma is studied using the data collected by the L3 detector at LEP. New results, corresponding to an integrated luminosity of 427.4 pb-1 at centre-of-mass energies from 192 GeV to 207 GeV, are presented. The W+W- gamma cross sections are measured to be in agreement with Standard Model expectations. No hints of anomalous quartic gauge boson couplings are observed. Limits at 95% confidence level are derived using also the process e+e- --> nu nubar gamma gamma
Measurement of W polarisation at LEP
No full textThe three different helicity states of W bosons produced in the reaction e(+)e(-) --\u3e W+W- --\u3e lvqq\u27 at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies roots = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 +/- 0.027 +/- 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation. (C) 2003 Published by Elsevier Science B.V
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