In this paper it is shown how a sampling electromagnetic calorimeter based on the liquid argon technique satisfies the very demanding requirements of an experiment at the LHC. Section 2 discusses, using a simplified model, the performance that can be achieved in terms of response time, energy resolution and transverse granularity. Section 3 describes how the calorimeters are realized in ATLAS, their segmentation and how from the readout pulses the energy deposited in the calorimeter is computed. The motivations of a presampler detector in front of the calorimeter are also discussed. Section 4 describes how the energy, position and direction of an electron and a photon are computed. Finally, Sec. 5 briefly illustrates the rejection power of the calorimeter against the hadrons and mentions how a Higgs boson signal in the γγ channel can already be detected with a luminosity of 10 fb-1.
Role of the CMS Electromagnetic Calorimeter in the hunt for the Higgs boson in the two-gamma channel
