The CMS Magnet Test and Cosmic Challenge

During the second half of 2006 a first combined test of almost all sub-systems of the Compact Muon Solenoid (CMS) experiment at CERN's new Large Hadron Collider has been performed. This test has been carried out in a surface assembly hall prior to the currently ongoing installation in the underground experimental cavern. Partial configurations of the CMS sub-detectors have been successfully interfaced with a scaled-down setup of the central Data Acquisition and Run Control systems, with the Level-1 Trigger and with the Detector Control and Safety Systems. The superconducting solenoid has been stably operated at its design field strength of 4 T. Several millions of events were reconstructed, stored and transferred to the Tier-0 computing centre and to remote sites. The present paper reports this first operation of CMS as an integrated system.