477 research outputs found
Search for Standard Model Higgs Boson in the ATLAS experiment
No full textThe recent results for searches for the Standard Model Higgs boson at a center of mass energy of 7 TeV using 4.9 fb−1 of data collected with the ATLAS detector at CERN Large Hadron Collider are presented. The data were taken during 2011 year
Studies of the underlying event with ATLAS
No full textParticle distributions sensitive to the underlying even have been measured with the ATLAS detector at the LHC. Charged particle multiplicity, charged and inclusive sum transverse momentum (pT) densities and mean charged-particle pT in the regions of each event, azimuthally transverse to the hardest jet, are also presented. When compared to the predictions of different Monte Carlo models, the data show sensitivity to the modelling of the underlying event
Analysis of Test-beam Data, Obtained with Module Zero of Hadron End-Cap Calorimeter
No full textBeam tests of the module zero of the LAr hadron end-cap calorimeter were carried out during two periods in April and August 1998. The results of the analysis of data, obtained with electron and pion beams are presented in the note
Performance of ATLAS End-Cap Calorimetry in the Transition Region between the Hadron End-Cap Calorimeter and the Forward Calorimeter
No full textAuthor Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
No full textIn the version of this article initially published, the ATLAS Collaboration
author names, affiliations and acknowledgements were omitted and
have now been included in the HTML and PDF versions of the article
Study of Influence of Large Ionization Rates on the Performance of ATLAS Endcup Hadronic LAr Calorimeter
No full textReliability Engineering for ATLAS Petascale Data Processing on the Grid
No full textThe ATLAS detector is in its third year of continuous LHC running taking data for physics analysis. A starting point for ATLAS physics analysis is reconstruction of the raw data. First-pass processing takes place shortly after data taking, followed later by reprocessing of the raw data with updated software and calibrations to improve the quality of the reconstructed data for physics analysis. Data reprocessing involves a significant commitment of computing resources and is conducted on the Grid. The reconstruction of one petabyte of ATLAS data with 1B collision events from the LHC takes about three million core-hours. Petascale data processing on the Grid involves millions of data processing jobs. At such scales, the reprocessing must handle a continuous stream of failures. Automatic job resubmission recovers transient failures at the cost of CPU time used by the failed jobs. Orchestrating ATLAS data processing applications to ensure efficient usage of tens of thousands of CPU-cores, reliability engineering minimizes the reprocessing duration and failure recovery costs. In 2010 reprocessing, the cost to recover transient failures was 6% of the CPU time used for reconstruction. In 2011 reprocessing, the cost used to recover transient failures was reduced to 4% of the CPU time used for the reconstruction. We present reliability engineering analysis of the ATLAS petascale data processing on the Grid
Recent Results on Soft QCD Topics from ATLAS
No full textThe ATLAS collaboration has performed several measurements in special data sets with low LHC beam currents, recorded at a center-of-mass energy of 13 TeV: Measurements of the inclusive charged-particle multiplicity and its dependence on transverse momentum and pseudorapidity are presented and compared with predictions of various MC generators. The collaboration has also performed measurements of the number and transverse-momentum sum of charged particles as a function of properties of the leading high pT track in the event at a center-of-mass energy of 13 TeV. The results are compared to predictions of several MC generators. In addition, the total inelastic proton-proton cross section and the diffractive part of the inelastic cross section was measured, using special forward scintillators or the calorimeters. The latter result completes the measurement of the elastic pp cross section in a dedicated run with high beta* optics at 8 TeV centre-of-mass energy with the ALFA Roman Pot detector. From the extrapolation of the differential elastic cross section to t=0, using the optical theorem, the total cross section is extracted with the luminosity-dependent method with high precision. Furthermore, the nuclear slope of the elastic t-spectrum and the total elastic and inelastic cross sections are determined. Finally, the collaboration has studied the hard double parton interactions (DPI) in events with 4 hadronic jets and translated into a measurement of the effective DPI cross section. Several DPI-sensitive variables are unfolded to particle level and compared to predictions of different MC models
Measuring Jet substructure observables at the ATLAS experiment
No full textJet substructure observables have significantly extended the search program for physics beyond the Standard Model at the Large Hadron Collider. The state-of-the-art tools have been motivated by theoretical calculations, but there has never been a direct comparison between data and calculations of jet substructure observables that are accurate beyond leading-logarithm approximation. Such ob- servables are significant not only for probing the collinear regime of QCD that is largely unexplored at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. The ATLAS collaboration has recently per- formed several measurements of precision jet substructure at 13 TeV that will significantly extend our understanding of both the perturbative and non-perturbative aspects of jet formation. These measurements of jet mass in various topologies as well as other properties of jet fragmentation such as charged-particle multiplicity and the properties of gluon splitting to bottom quarks are unfolded to correct for detector effects and compared with a variety of predictions
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