A module of the ATLAS electromagnetic barrel liquid argon calorimeter was exposed to the CERN electron test-beam at the H8 beam line upgraded for precision momentum measurement. The available ...energies of the electron beam ranged from 10 to 245
GeV. The electron beam impinged at one point corresponding to a pseudo-rapidity of
η
=
0.687
and an azimuthal angle of
φ
=
0.28
in the ATLAS coordinate system. A detailed study of several effects biasing the electron energy measurement allowed an energy reconstruction procedure to be developed that ensures a good linearity and a good resolution. Use is made of detailed Monte Carlo simulations based on GEANT4 which describe the longitudinal and transverse shower profiles as well as the energy distributions. For electron energies between 15 and 180
GeV the deviation of the measured incident electron energy over the beam energy is within 0.1%. The systematic uncertainty of the measurement is about 0.1% at low energies and negligible at high energies. The energy resolution is found to be about 10%
·
E
for the sampling term and about 0.2% for the local constant term.
Response uniformity of the ATLAS liquid argon electromagnetic calorimeter Aharrouche, M.; Colas, J.; Di Ciaccio, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2007, Letnik:
582, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The construction of the ATLAS electromagnetic liquid argon calorimeter modules is completed and all the modules are assembled and inserted in the cryostats. During the production period four barrel ...and three endcap modules were exposed to test beams in order to assess their performance, ascertain the production quality and reproducibility, and to scrutinize the complete energy reconstruction chain from the readout and calibration electronics to the signal and energy reconstruction. It was also possible to check the full Monte Carlo simulation of the calorimeter. The analysis of the uniformity, resolution and extraction of constant term is presented. Typical non-uniformities of
5
‰
and typical global constant terms of
6
‰
are measured for the barrel and endcap modules.
The response of the ATLAS electromagnetic calorimeter to muons has been studied in this paper. Results on signal over noise ratio, assessment of the detector response uniformity, and position ...resolution are presented. The possibility to study fine details of the structure of the detector through its response to muons is illustrated on a specific example. Finally, the performance obtained on muons in test-beam is used to estimate the detector uniformity and time alignment precision that will be reachable after the commissioning of the ATLAS detector with cosmic rays.
The time reconstruction performance of the ATLAS electromagnetic calorimeter readout is studied. The contribution of the electronics to the time resolution is estimated to be about 20
ps, thus ...demonstrating the possibility of achieving a small constant term in the time resolution for particles. The resolution to electromagnetic showers produced by an electron beam is also measured. After correction for the effects due to the calorimeter geometry, a 100
ps constant term is found for a typical cell.
One universal extra dimension in Pythia ElKacimi, M.; Goujdami, D.; Przysiezniak, H. ...
Computer physics communications,
01/2010, Letnik:
181, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Universal Extra Dimensions model has been implemented in the
Pythia generator from version 6.4.18 onwards, in its minimal formulation with one TeV
−1-sized extra dimension. The additional ...possibility of gravity-mediated decays, through a variable number of eV
−1-sized extra dimensions into which only gravity extends, is also available. The implementation covers the lowest lying Kaluza–Klein (KK) excitations of Standard Model particles, except for the excitations of the Higgs fields, with the mass spectrum calculated at one loop.
2
→
2
tree-level production cross sections and unpolarized KK number conserving 2-body decays are included. Mixing between iso-doublet and -singlet KK excitations is neglected thus far, and is expected to be negligible for all but the top sector.
Program title: PYTHIA Version number: 6.420
Catalogue identifier: ACTU_v2_1
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ACTU_v2_1.html
Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence,
http://cpc.cs.qub.ac.uk/licence/licence.html
No. of lines in distributed program, including test data, etc.: 79 362
No. of bytes in distributed program, including test data, etc.: 590 900
Distribution format: tar.gz
Programming language: Fortran 77
Computer: CERN lxplus and any other machine with a Fortran 77 compiler
Operating system: Linux Red Hat
RAM: about 800 K words
Word size: 32 bits
Classification: 11.2
Catalogue identifier of previous version: ACTU_v2_0
Journal reference of previous version: Comput. Phys. Comm. 135 (2001) 238
Does the new version supersede the previous version?: Yes
Nature of problem: At high energy collisions between elementary particles, physics beyond the Standard Model is searched for. Many models are being investigated, namely extra-dimensional models.
Solution method: The Universal Extra Dimension model is implemented in the PYTHIA event generator.
Reasons for new version: The Universal Extra Dimensions model has been implemented in the PYTHIA generator from version 6.4.18 onwards, in its minimal formulation with one TeV
−1-sized extra dimension. The additional possibility of gravity-mediated decays, through a variable number of eV
−1-sized extra dimensions into which only gravity extends, is also available. The implementation covers the lowest lying Kaluza–Klein (KK) excitations of Standard Model particles, except for the excitations of the Higgs fields, with the mass spectrum calculated at one loop.
2
→
2
tree-level production cross sections and unpolarized KK number conserving 2-body decays are included. Mixing between iso-doublet and -singlet KK excitations is neglected thus far, and is expected to be negligible for all but the top sector.
Running time: 10–1000 events per second, depending on the process studied.
The ATLAS liquid argon calorimeter read-out system Bazan, A.; Bellachia, F.; Blondel, A. ...
IEEE Transactions on Nuclear Science,
06/2006, Letnik:
53, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The Liquid Argon calorimeters play a central role in the ATLAS experiment. The environment at the LHC collider imposes challenging tasks to their read-out system. To achieve measurements of particles ...and trigger signals at high precision, the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ). Signals from the calorimeter cells are received by front-end boards, which digitize and sample the incoming pulse. Read-out Driver (ROD) boards further process the data at a trigger rate of up to 75 kHz. An optimal filtering procedure is applied to optimize the signal-to-noise ratio. The ROD boards calculate precise energy, time and quality of the detector pulse, which are then sent to the DAQ. In addition, the RODs perform a monitoring of the data. The architecture of the ATLAS Liquid Argon detector read-out is discussed, in particular the design and functionality of the ROD board. Performance results obtained with ROD prototypes as well as experience from complete test setups with final production boards are reported.
Thin scintillating tiles with high light yield for the OPAL endcaps Aguillion, G.; Anderson, B.; Attree, D.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1998, Letnik:
417, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Arrays of thin scintillating tiles with embedded wavelength shifting fibre readout have been installed in the OPAL endcaps to improve trigger performance, time resolution and hermeticity for ...experiments at LEP II. The arrays were required to have high single-particle detection efficiency, uniform response, low noise and good time resolution. Limited space for the detector, and a strong magnetic field in the endcap region, resulted in a need for high light output per unit thickness of scintillator, and remote readout. In addition, because of limited space for readout cables, a high light yield per embedded fibre was required. This paper describes the design and construction of a tile array that satisfies these requirements. A light yield of 14 photoelectrons per minimum ionizing particle and a time resolution of 3
ns were obtained during 1997 LEP operation.
Searches are performed for resonant and non-resonant Higgs boson pair production in the hh to gamma gamma b bbar final state using 20 fb-1 of proton--proton collisions at a center-of-mass energy of 8 ...TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of non-resonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The corresponding limit observed for a narrow resonance ranges between 0.8 and 3.5 pb as a function of its mass.
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