Status and commissioning of the ATLAS experiment at the LHC

The ATLAS experiment (A Toroidal LHC ApparatuS) is one of the two general purpose detectors (CMS is the other) at the Large Hadron Collider, at CERN (Geneva). It is designed to study p-p collision at a center of mass energy of √(s)=14TeV and at a luminosity of 1034cm-1s-1. ATLAS with its dimensions, 46 m long, 25 m in diameter and a weight of about 7000 ton is the biggest collider experiment ever built. The project has involved roughly 2000 scientists and engineers of 165 institutions in 35 countries. The installation in the underground cavern is scheduled to be completed in July 2008 to be ready for the initial p-p collisions at a center of mass energy of √(s)=10TeV by late summer 2008. The detector design has been optimized to cover the largest possible search of new physics at the LHC energy: Higgs bosons and alternative schemes for the spontaneous symmetry-breaking mechanism; supersymmetric particles, new gauge bosons, leptoquarks, quark and lepton compositeness, extra dimensions. At the same time high-precision measurements of Standard Model processes will be performed and this will allow more stringent tests of the present electroweak theory and an indirect search for physics beyond the Standard Model. This paper presents a comprehensive overview of the ATLAS detector prior to the first LHC collisions.