HLT Track Selection in CMS

CMS running on its peak has collisions of bunches every 25 ns. Each bunch is consist of about 1011 protons. At each collision there are around 25 events in 2012 LHC and it will be around 40 events in Run II. So the event rate is around 1 GHz (109 Hz). This huge amount of data cannot be stored for later analysis with current devices. Also interesting physics is rare and usually occurs in 10 Hz . So a reduction of several orders of magnitude in event rate is needed.