Characteristics of the ATLAS and CMS detectors.

The goal for the detection of new physics processes in particle collisions at Large Hadron Collider energies, combined with the broad spectrum of possibilities for how the physics might be manifest, leads to detectors of unprecedented scope and size for particle physics experiments at colliders. The resulting two detectors, ATLAS (A Toroidal LHC ApparatuS) and CMS (compact muon spectrometer), must search for the new physics processes within very complex events arising from the very high-energy collisions. The two experiments share many basic design features-in particular, the need for very selective triggering to weed out the bulk of the uninteresting events; the order in which detector types are arrayed in order to provide maximum information about each event; and the very large angular coverage required to constrain the energy carried by any non-interacting particles. However, within these basic constraints, the detectors are quite different given the different emphases placed on issues such as resolution and background rejection. Both common features and the distinct differences will be presented.