Electron and photon measurement will play a key role in Higgs boson hunting and new physics searches. CPPM is therefore heavily involved in the ATLAS electromagnetic calorimeter. It is a sampling calorimeter with liquid argon as active medium and accordion shaped lead plates as absorber. The lab was responsible for the building of the two end-caps of this system. Each is a 4 meter diameter wheel, weighting 27 tons and read-out by 31872 channels. The construction started at CPPM in August 2001, and the last piece was delivered in March 2004. After the final assembly at CERN, the two end-caps were installed in the experimental cavern and are operating since 2006.

The CPPM group now actively participates to the final qualification and commissionning of the whole electomagnetic calorimeter. Test beam analyses allowed to perform a first calibration, to check the in-situ performance and to improve simulation codes. All this is now refined with analysis of cosmic data. Moreover, the data resulting from the passing of the first LHC beams through ATLAS in September 2008 was carefully analysed and allowed to further improve the detector response understanding. The calorimeter is now ready to measure the energy flow which will be created by LHC proton collisions.

For further information on electomagnetic calorimetry (in french), see ATLAS-France URL