Triggers and streams for calibration in CMS

Sustained operation of the CMS detector requires feeding the calibration workflows with precisely the information that is needed for optimal determination of the constants. Beyond the regular data streams used for physics analysis, the CMS experiment maintains various data streams that are dedicated for calibration purposes. This includes streams collecting data produced by hardware calibration systems. Some calibrations requiring particularly high events rates are driven by special data streams that select the relevant event fractions already at the HLT level, for example π0 and η candidates for the intercalibration of the electromagnetic calorimeter. A dedicated express stream drives very low latency workflows that are operated at the CERN Analysis Facility. In many cases, dedicated triggers are essential to select the appropriate event types and build the corresponding streams. Experience from operating this system during the ramp-up of LHC luminosity in spring 2010 is presented.