Abstract
In December 2009 the ATLAS experiment at the CERN Large Hadron Collider (LHC) recorded the first proton-proton collisions at a centre-of-mass energy of 900 GeV, followed by the unprecedented energy of 7 TeV in March 2010. The Semi-Conductor Tracker (SCT) is a key precision tracking device in ATLAS, made of p-in-n-type silicon micro-strip detectors. The completed SCT has been installed inside the ATLAS experimental hall. After the commissioning phase it was in very good shape for the first LHC collision runs: 99.3% of the SCT strips are operational, noise occupancy and hit efficiency exceed the design specifications, and the alignment is already close enough to the ideal one to allow on-line track reconstruction and invariant mass determination. This paper reviews the current status of the SCT, including results from the latest data-taking periods in 2009 and 2010, and from the detector alignment. The operation of the detector and observed problems are discussed, with emphasis on the performance of the SCT with the LHC in collision mode in comparison with the expected parameters and with the Monte Carlo simulations.
Highlights
After years of installation, commissioning and data-taking with cosmics, we are taking real collision data!
ATLAS has been designed to be sensitive to as wide a range of potential new physics as possible
The second layer of the Inner Detector, the Semi-Conductor Tracker occupies the region from 30 to 52 cm radially from the interaction point and reaching to ±2.7 m in the zdirection, providing tracking coverage up to |η|=2.5
Summary
ATLAS is one of two large, general-purpose detectors at CERN's Large Hadron Collider (LHC) with the aim of searching for new particles and processes, such as Supersymmetry or the elusive Higgs boson. ATLAS has been designed to be sensitive to as wide a range of potential new physics as possible. Starting from the interaction point and moving outwards:. The Pixel detector The Semi-Conductor Tracker (SCT) The Transition Radiation Tracker (TRT). The Electromagnetc Liquid Argon Calorimeter The Hadronic Tile Calorimeter The Muon Spectrometer. Collisions at the LHC: 23/11/2009: First collisions at the LHC (900 GeV) 8/12/2009: Collisions at 2.36 TeV (world record) 30/3/2010: Collisions at 7 TeV! Plan to collect 1 fb-1 in 2010-2011. After years of installation, commissioning and data-taking with cosmics, we are taking real collision data!
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