Design for a L1 tracking trigger for CMS

We present an electronics design for a tracking trigger for the CERN SLHC. The on detector part uses asynchronous logic so the only clock required is the LHC crossing clock. High Pt tracks are identified with a hierarchical method that finds track stubs using closely spaced pairs of detectors. Track segments (called tracklets) are then formed from pairs of stubs that are separated by 40 mm. This separation is close enough so that matching stubs is relatively easy but far enough apart so that the tracklets can be projected to another layer with mm accuracy. Matching segments in two or more layers then define a track.