A Roadmap for HEP Software and Computing R&D for the 2020s

Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.Peer reviewe

Latest ATLAS measurements of top quark properties using ttˉ{\rm t{\bar t}} events

International audienceRecent measurements of top quark properties with ${\rm t{\bar t}}$ events collected by the ATLAS experiment in proton-proton collisions at the center of mass energy $\sqrt{s}=8$ and $13$ TeV, are presented. The measurements of the top quark width, spin and spin correlations, polarisation, the $W$ boson helicity fractions, charge and CP asymmetries are discussed. Finally, recent results obtained on colour flow effects in ${\rm t{\bar t}}$ events are presented. All the measurements are consistent with the Standard Model expectations

Top quark measurements in ATLAS

International audienceThe top quark is the heaviest elementary particle known and its mass is a fundamental parameter of the Standard Model. The main theoretical and experimental challenges related to this measurement are presented. Masses from different ATLAS measurements are in good agreement within uncertainties. Precision of the measurements with the directly measured top-quark mass is now better than 0.5%. Progress in determination of the top-quark pole mass is reported and the relation between the directly measured top-quark mass and top-quark pole mass is discussed. Related measurements allowing for better tuning of modelling uncertainties are also presented.Finally, ideas and prospects for the improvement of the precision of this measurement during the upcoming LHC runs are briefly outlined

b-fragmentation studies in tt ̄ events in ATLAS and CMS

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Recherche d'événements de microlentille gravitationnelle dans les bras spiraux de la galaxie avec EROS II

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Reconstruction et identification des électrons dans l'expérience Atlas. Participation à la mise en place d'un Tier 2 de la grille de calcul

The origin of the mass of elementary particles is linked to the electroweak symmetry breaking mechanism. Its study will be one of the main efforts of the ATLAS experiment at the Large Hadron Collider of CERN, starting in 2008. In most cases, studies will be limited by our knowledge of the detector performances, as the precision of the energy reconstruction or the efficiency to identify particles. This manuscrit of habilitation presents a work dedicated to the reconstruction of electrons in the ATLAS experiment with simulated data and data taken during the combined test beam of 2004. The analysis of the ATLAS data implies the use of a huge amount of computing and storage resources which brought to the development of a world computing grid. This manuscrit presents also the effort done at the LPNHE Paris for the setup of a Tier 2 in the grand Paris area.L'origine de la masse des particules élémentaires est liée au mécanisme de brisure de la symétrie électrofaible. Son étude sera l'un des enjeux majeurs de l'expérience Atlas auprès du Large Hadron Collider, au Cern à partir de 2008. Dans la plupart des cas, les recherches seront limitées par notre connaissance des performances du détecteur, telles que la précision avec laquelle l'énergie des particules est reconstruite ou l'efficacité avec laquelle elles sont identifiées. Ce mémoire d'habilitation présente un travail portant sur la reconstruction des électrons dans Atlas avec des données simulées et des données prises durant le test en faisceau combiné qui s'est déroulé en 2004. L'analyse des données d'Atlas nécessite l'utilisation de ressources de calcul et de stockage importantes qui a impliqué le développement d'une grille de calcul mondiale dont un des noeuds est développé au laboratoire. Le manuscrit présente aussi l'effort effectué au LPNHE Paris pour la mise en place d'un Tier 2 en r\égion Ile de France

ATLAS usage of GPU

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Identification and use of low p_T electrons with Rome data

ATLAS internal noteIdentification and use of low p_T electrons with Rome data / Cochran, J ; Derue, F ; Kaczmarska, A ; Wolter, M This note describes the perfomance obtained with the low p_T electron reconstruction algorithm with Rome data. The algorithm is used on WH, H->bb, uu and J/psi->e+e- events

Search for a Standard Model Higgs boson in the ATLAS experiment on the H channel

ATLAS internal noteThis note deals with the search for a Standard Model Higgs boson on the H channel in the ATLAS experiment at the Large Hadron Collider (LHC). Di-photon signal and background are investigated using Next to Leading order (NLO) calculation

Investigating the possibility of the top quark mass measurement with the matrix element method in the dilepton final state with the ATLAS detector at the LHC

21 pATLAS internal communicationThis note presents the use of the matrix element method for a measurement of the top quark mass in the dilepton channel in ATLAS. The matrix element method is well designed for a top mass measurement with only few selected events, hence it is well adapted to the LHC first data