Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons
European Physical Journal C 70:3 (2010) 755-785
Abstract:
The ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons. In particular, the drift time of the ionization electrons is measured and used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. The drift times of electrons in the cells of the second layer of the calorimeter are uniform at the level of 1.3% in the barrel and 2.8% in the endcaps. This leads to an estimated contribution to the constant term of (0.290.040.05)% in the barrel and (0.540.040.06)% in the endcaps. The same data are used to measure the drift velocity of ionization electrons in liquid argon, which is found to be 4.61±0.07 mm/μs at 88.5 K and 1 kV/mm. © 2010 CERN for the benefit of the ATLAS collaboration.Events with an isolated lepton and missing transverse momentum and measurement of W production at HERA
Journal of High Energy Physics 2010:3 (2010)
Abstract:
A search for events containing an isolated electron or muon and missing transverse momentum produced in e±p collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 1994-2007 and correspond to an integrated luminosity of 0.98 fb-1. The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single W production. In the e+p data, at large hadronic transverse momentum PTX < 25GeV, a total of 23 events are observed compared to a prediction of 14.0 ±1.9. The total single W boson production cross section is measured as 1.06 ± 0.16 (stat.) ± 0.07 (sys.) pb, in agreement with an Standard Model (SM) expectation of 1.26 ± 0.19 pb.Fine synchronization of the CMS muon drift-tube local trigger using cosmic rays
Journal of Instrumentation 5:3 (2010)
Abstract:
The CMS experiment uses self-triggering arrays of drift tubes in the barrel muon trigger to perform the identification of the correct bunch crossing. The identification is unique only if the trigger chain is correctly synchronized. In this paper, the synchronization performed during an extended cosmic ray run is described and the results are reported. The random arrival time of cosmic ray muons allowed several synchronization aspects to be studied and a simple method for the fine synchronization of the Drift Tube Local Trigger at LHC to be developed. © 2010 IOP Publishing Ltd and SISSA.First measurement of the underlying event activity at the LHC with √ = 0.9 TeV
European Physical Journal C 70:3 (2010) 555-572
Abstract:
A measurement of the underlying activity in scattering processes with pT scale in the GeV region is performed in proton-proton collisions at √ = 0.9 TeV, using data collected by the CMS experiment at the LHC. Charged particle production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged particles with pseudorapidity {pipe}η{pipe} < 2, pT > 0.5 GeV/c, and azimuthal direction transverse to that of the leading object. © 2010 CERN for benefit of the CMS collaboration.From the LHC to future colliders
European Physical Journal C 66:3 (2010) 525-583