The ATLAS calorimeter trigger commissioning using cosmic ray data

While waiting for the first LHC collisions, the ATLAS detector is undergoing integration exercises performing cosmic ray data taking runs. The ATLAS detector is a general purpose detector consisting of inner tracker, calorimetry and muon spectrometer. The ATLAS calorimeter trigger software uses a common framework capable of retrieving, decoding and providing data to different particle identification algorithms. This work reports on the results obtained during the first data-taking period of 2009 with the calorimeter trigger. Experts from detector areas such as calorimetry, data flow management, data quality monitoring and the trigger worked together to reach stable data taking conditions. Issues like noise readout channels were addressed and the global trigger robustness was evaluated. It is confirmed that the level 2 trigger timing requirement is satisfied and that its behavior, such as η dependence, is as expected