Design process of the CMS Silicon Tracker for Super-LHC

Following an expected increase of the LHC luminosity beyond its design value of 1034 cm􀀀2s􀀀1 the CMS collaboration is planning for a series of upgrades on the experimental apparatus. In particular the silicon tracker should undergo two major upgrades to cope with the increased luminosity of the collider. The first intervention (Phase I) concerns a replacement of the pixel system, the rest of the tracker being untouched. A second major upgrade (Phase II) consists of a full replacement of the entire silicon tracker to cope with the foreseen ultimate SLHC luminosity (1035 cm􀀀2s􀀀1). In these extreme conditions several hundred of interactions per beam crossing are expected and the number of charged particles generated will correspondingly increase with respect to the LHC conditions, requiring a new detector with a much higher granularity. This should be achieved keeping both the tracker power consumption and the material budget at levels which will not jeopardize the instrument operability and perfomance. Furthermore, the radiation tolerance of the new silicon sensors should be much higher than the present ones, requiring major developments on the detector technology side. Finally, the new tracker should be able to provide data to contribute to the CMS first level trigger. Possible layouts of the new tracking system have to be simulated in detail to understand the behaviour of the apparatus in a very high pile-up condition and to define a new optimal design which could meet the SLHC requirements. In these proceedings the CMS silicon tracker upgrades will be described, with a special emphasis on Phase I pixel system, Phase II tracker and first level track trigger.