Use of associative memories for L1 triggering in LHC environment

The CDF Associative-Memory device (AM), proven technology developed for the Silicon-Vertex-Trigger at the CDF experiment, is one of the proposed solutions at LHC for track reconstruction at level-1 in the HL-LHC upgrade, for very high-luminosity conditions (hundreds proton-proton collisions every 25 ns, at 5 × 1034 cm−2sec−1). This luminosity requires a drastic revision of the existing trigger strategies. In the framework of the CMS experiment, one of the identified challenges for future upgrades is the capability of using already at L1 the tracker information to trigger events. This strategy requires massive computing power to minimize the online execution time of complex tracking algorithms and the ``combinatorial challenge''. The AM allows to compare the tracker information of each event to pre-calculated ``expectations'' (pattern matching) in such a short time that tracks can contribute to the trigger decision. One of the main challenges for the CMS tracker is the latency due to the tracker data distribution to the AM processors. A very parallelized readout architecture and a possible layout are discussed.