Validation Studies of the ATLAS Pixel Detector Control System

The ATLAS pixel detector consists of 1744 identical silicon pixel modules arranged in three barrel layers providing coverage for the central region, and three disk layers on either side of the primary interaction point providing coverage of the forward regions. Once deployed into the experiment, the detector will employ optical data transfer, with the requisite powering being provided by a complex system of commercial and custom-made power supplies. However, during normal performance and production tests in the laboratory, only single modules are operated and electrical readout is used. In addition, standard laboratory power supplies are used. In contrast to these normal tests, the data discussed here was obtained from a multi-module assembly which was powered and read out using production items: the optical data path, the final design power supply system using close to final services, and the Detector Control System (DCS). To demonstrate the functionality of the pixel detector system a stepwise transition was made from the normal laboratory readout and power supply systems to the ones foreseen for the experiment, with validation of the data obtained at each transition.Comment: 8 pages, 8 figures, proceedings for the Pixel2005 worksho

ATLAS Pixel Detector Timing Optimisation with the Back of Crate Card of the Optical Pixel Read out System

As with all detector systems at the Large Hadron Collider (LHC), the assignment of data to the correct bunch crossing, where bunch crossings will be separated in time by 25 ns, is one of the challenges for the ATLAS pixel detector. This document explains how the detector system will accomplish this by describing the general strategy, its implementation, the optimisation of the parameters, and the results obtained during a combined testbeam of all ATLAS subdetectors

Optical Readout in a Multi-Module System Test for the ATLAS Pixel Detector

The innermost part of the ATLAS experiment at the LHC, CERN, will be a pixel detector. The command messages and the readout data of the detector are transmitted over an optical data path. The readout chain consists of many components which are produced at several locations around the world, and must work together in the pixel detector. To verify that these parts are working together as expected a system test has been built up. In this paper the system test setup and the operation of the readout chain is described. Also, some results of tests using the final pixel detector readout chain are given.Comment: 6 pages, 10 figures, Pixel 2005 proceedings preprin

Towards the final ATLAS Pixel Detector Control System

The innermost part of the ATLAS experiment is a pixel detector, built by 1744 individual detector modules. To operate the modules, readout electronics, and other detector components, a complex power supply and detector control system (DCS) is necessary. This includes a large number of crates, which house the different hardware components as well as a PC net where the different control projects are running. To test the final detector after its assembly before it is installed in the ATLAS cavern, a large test system has been set up at CERN, which allows to operate ca. 10 % of the detector in parallel. Since autumn 2006 this system is in permanent operation. As nearly everywhere the final control hardware is used, its reliability could be investigated and the performance of the control software could be studied. After an overview on our DCS hardware, we report on the experience with the control software

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration