184 research outputs found
Alignment of the inner detector and of the muon system of the ATLAS experiment
No full textAlignment of the ATLAS inner detector tracking system Large Hadron Collider (LHC) at CERN is the world's largest particle accelerator. After a successful start run at 900 GeV in 2009, during 2010, LHC will collide two proton beams at an unprecedented center of mass energy of 7 TeV. ATLAS is one of the four multipurpose experiments that will record the products of the LHC proton-proton collisions. ATLAS is equipped, along others, with a charged particle tracking system built on two different technologies: silicon sensors and drift-tube based detectors constituting the ATLAS Inner Detector (ID). In order to achieve its scientific goals, ATLAS has quite exigent tracking performance requirements. Thus, the goal of the alignment is set such that the limited knowledge of the sensors location should not deteriorate the resolution of the track parameters by more than 20% with respect to the intrinsic tracker resolution. In this manner the required precision for the alignment of the silicon sensors in its most sensitive direction is below 10 micrometers. The alignment of the ATLAS tracking system requires the determination of almost its 36000 degrees of freedom with high accuracy. This demands to use a large sample of high momentum and isolated charged particle tracks. A track based alignment approach has been implemented in the ATLAS software framework as well as a description of the detector geometry that accounts for assembly struct ures and individual modules. A frequency scanning interferometer (FSI) system is also run to monitor the stability of the silicon strip detector structures. Data with FSI system has been recorded and analyzed and show how stable the detector is and its response to events that affect the detector operation. We will present the outline of the track based alignment approaches, their code implementation within the ATLAS computing framework and their results when aligning the real detector. So far the proposed alignment algorithms have been applied to the real data recorded from both: the LHC collisions and cosmic ray data as well. Results will be shown using 2009 and 2010 LHC data. Finally the impact of the alignment on physics measurements will be discussed. Alignment of the ATLAS muon spectrometer The muon spectrometer of the ATLAS experiment at the Large Hadron Collider at CERN is designed to measure muon momenta of up to 1 TeV with a resolution of better than 10%. It consists of three layers of precision drift tube chambers located in a toroidal field of superconducting air-core magnets. To achieve the desired momentum resolution with the 3-point track sagitta measurement, the muon chambers have to be aligned with an accuracy of better than 30 micro-meter in the track bending plane. Muon chamber movements are monitored by an optical alignment system with a precision of several microns. Initial chamber positions have to be deter mined with a straight muon tracks from cosmic rays and from proton-proton collisions in a dedicated run of the ATLAS detector with the toroid magnets switched off. A least-square corrections are used for the muon reconstruction during the ATLAS data taking. The combination of track-based and optical alignment procedures allows to achieve the required level of accuracy
Alignment of the Inner Detector and of the Muon Spectrometer of the ATLAS experiment
No full textThe ATLAS experiment at the Large Hadron Collider at CERN is equipped with two tracking systems: the Inner Detector and the Muon Spectrometer. To achieve the desired tracking performance, these subdetectors have to be aligned with the precision of better than 10 micrometers for the Inner Detector and of better than 30 micrometers for the Muon Spectrometer. Track based alignment approaches in combination with optical sensor measurements are used to fullfill these requirements. The alignment corrections have been successfully applied to the LHC collision data. The results show that the precision of current alignment already allows for a good tracking performance
Search for excited electrons and muons in √s = 8 TeV proton–proton collisions with the ATLAS detector
No full textThe ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp! ! , assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb−1 of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excitedlepton mass m` . For m` > 0.8 TeV, the respective upper limits on B( ) are 0.75 and 0.90 fb for the e and μ searches. Limits on B are converted into lower bounds on the compositeness scale 3. In the special case where 3 = m` , excited-electron and excited-muon masses below 2.2 TeV are excluded
The Alignment System of the ATLAS Barrel Muon Spectrometer
No full textThe alignment system of the ATLAS barrel muon spectrometer
Alignment of the ATLAS Muon Spectrometer with Tracks
No full textAlignment of the ATLAS muon spectrometer with tracks
Device for Measuring of Wire Tension in Drift Tubes
No full textA device for measuring the wire tension in wired detectors is presented. Its operational principle consists in the excitation of the signal wire oscillations in magnetic field with current pulses followed by determination of the main frequency of the wire free oscillations using Fourier analysis. The device allows to measure the wire tension both in separate drift tubes and in chambers assembled of them. The measurement accuracy is better than 0.05 %, and the measurement time is less than 5 seconds
Data Acquisition and Storage in the Production and Testing Process of Drift Tubes and MDTChambers for ATLAS Experiment at LNP, JINR, Production Site
No full textA description of how data from the drift tube semiautomatic wiring line and test stations, and data from the MDTchamber assembly process are acquared and stored at the specialized production site of the JINR ATLAS muon group is given. A general scheme of the data acquisition and storage process, as well as generic structure of the database, is presented
Search for a CP-odd Higgs boson decaying to Zh in pp collisions at root s=8 TeV with the ATLAS detector
No full textSee paper for full list of authors – 13 pages plus author list + cover pages (30 pages total), 5 figures, 2 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-06/International audienceA search for a heavy, CP-odd Higgs boson, , decaying into a boson and a 125 GeV Higgs boson, , with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. Decays of CP-even bosons to or pairs with the boson decaying to electron or muon pairs are considered, as well as decays with the boson decaying to neutrinos. No evidence for the production of an boson in these channels is found and the 95% confidence level upper limits derived for \sigma (gg\rightarrow A) \times \mbox{BR}(A \rightarrow Zh) \times \mbox{BR}(h \rightarrow f\bar{f}) are 0.098--0.013 pb for and 0.57--0.014 pb for in a range of 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models
Calibration Model for the MDT Chambers of the ATLAS Muon Spectrometer
No full textCalibration model for the ATLAS MDT chambers
- …
