CMS Tracker commissioning at the Magnet Test Cosmic Challenge
The so called Magnet Test Cosmic Challenge (MTCC) was the first comprehensive operational and functional test of the CMS experiment. the MTCC took place in the first months of 2006 and was a slice test in which a small fraction of all the CMS detection equipment was operated in the 4 T solenoid of the experiment. Cosmic rays detected in the muon chambers were used to trigger the readout of all detectors in the global CMS data acquisition system. Prior to data taking, the detectors and their readout electronics were tuned and synchronized with dedicated software procedures. Local reconstruction was carried out online and offline in all sub-detectors for event selection and monitoring purposes. Global reconstruction, linking different sub-detectors, was performed mainly offline. A number of monitoring and visualization tools were also used for validation purposes and monitoring. One of the main goals of the MTCC was the validation of the hardware alignment system functionality.
At the MTCC, UCL had a leading role in the preparation, operation and offline data analysis related to the silicon strip tracker detector.
Early observation of top quark pairs in the dileptonic final state
The top quark is the heaviest elementary particle discovered so far, and many properties related to this quark are still to be understood.
Its observation and mass measurement at Tevatron highlighted the uncommon nature of this quark. The fact that its electroweak decay is faster than the hadronization time scale implies that the top quark exists only as a free quark, so that the effects from new physics should show up very clearly by comparing measurements with the precise Standard Model preditions.
Its "re-discovery" at LHC will be a major milestone for the experiments, since the complexity of the final state demands a fairly good knowledge of the experimental apparatus and a certain degree of control of the backgrounds. Its expected large coupling to Higgs bosons will also be relevaant for the searches for higgs sectors beyond the Standard Model.
External collaborators: CMS collaboration.