Conceptual study of a trigger module for the CMS Tracker at SLHC

The CMS experiment is planning a major upgrade of its tracking system to adapt to an expected increase in luminosity of the LHC accelerator to 1035 cm-2 s-1. It will then have to cope with several hundred interactions per bunch crossing and fluxes of thousands of charged particles emerging from collisions. CMS requires tracker data to contribute to the first level trigger, to maintain the present 100 kHz rate while increasing the trigger decision latency by only a few μs. It must be achieved without compromising the tracking performance which is very sensitive to the material budget. A key part of a system to achieve this will be the design of a suitable module to generate trigger primitives. One possible solution is based on the so-called 'stacked tracker modules' using closely spaced, coarsely pixilated sensor layers situated at intermediate radius within the tracker volume. The pattern of hits in each layer is compared to identify high pT track candidates. Simulations have been carried out which support the basic concept. A basic readout architecture is proposed and some of the electronic implications are described. Estimates of likely power consumption are given, as well as data rates and link bandwidth requirements.