The ATLAS experiment at the LHC will explore a large spectrum of physics channels within and beyond the Standard Model (SM) of the particle physics. The search for the Higgs boson (the missing piece of the SM), and for new physics expected at the TeV scale within models like supersymmetry, extra dimensions or grand unified theories will be among the most studied physics topics. The measurement of the SM parameters from electroweak and strong interaction processes (W mass, mass and couplings of the top quark, WWg, WWZ couplings, cross section of different physics processes within the SM, ...) and b hadrons physics with measurements of CP violating processes and rare b hadrons decays, which are excellent indirect probes of physics beyond the SM, will also be studied and explored, and are complementary to direct searches. They will complement and improve our understanding of physics at the energy scale that will be explored by the LHC.
In the framework of the performances studies of the ATLAS detector and the preparation of the physics analysis during the first LHC phase, the ATLAS group was involved since many years in top quark physics through the spin correlation studies of the pair produced top quarks for the search of anomalous couplings between the top quark and the W boson, and also in the search for the standard Higgs boson in the associated production channels ttH(bb) et WH(bb) as well as the supersymmetric charged Higgs boson in the associated production channel tbH(tb). The group is also involved in the preparation of physics analysis channels with discovery potential in the early LHC data like high mass Z' et W'^± bosons decaying respectively into e⁺e^- et e^±&nu pairs and the search for supersymmetry in final states with Z boson and missing transverse energy. The measurement of the production cross section of the top-anti-top quark pairs is also among the priorities of the group with the early LHC data.
Conducting these analysis and studies efficiently requires an accurate understanding of the different ATLAS detector components. That is why the ATLAS group has been actively involved since many years in an important and systematic work of simulation, calibration and evaluation of the performances of the electromagnetic calorimeter and the pixel detector and in particular in the improvement of the electron-jets separation algorithms and of b-jets tagging for which the group is playing a leading role in the ATLAS collaboration. In all these analysis and studies, the group uses increasingly the distributed computing model on the world LHC grid (LCG).