Commissioning of the CMS Experiment and the Cosmic Run at Four Tesla

Understand

The CMS Collaboration conducted a month-long data-taking exercise known as the Cosmic Run At Four Tesla in late 2008 in order to complete the commissioning of the experiment for extended operation.

• The operational lessons resulting from this exercise were addressed in the subsequent shutdown to better prepare CMS for LHC beams in 2009.
• The cosmic data collected have been invaluable to study the performance of the detectors, to commission the alignment and calibration techniques, and to make several cosmic ray measurements.
• The experimental setup, conditions, and principal achievements from this data-taking exercise are described along with a review of the preceding integration activities.