The CMS trigger system must reduce an input data rate from the LHC
bunch-crossing frequency of 40 MHz to a rate which will be written to
permanent storage. This online event selection is performed in two
steps. At the first level (L1) the rate is reduced to 100 kHz, based on
calorimeter and muon trigger subsystem information. Then the selected events
are forwarded to the high level trigger (HLT), which further reduces the
rate to 100 Hz using sophisticated software.
The CMS experiment has collected over 300 million cosmic ray events.
This has provided an excellent opportunity to test the trigger and
prepare for the collision data. In this presentation, we show analysis
results from the cosmic ray trigger data and discuss about the
preparations for collision data taking