Abstract
In 2021 the LHCb experiment will be upgraded, and the DAQ system will be based on full reconstruction of events, at the full LHC crossing rate. This requires an entirely new system, capable of reading out, building and reconstructing events at an average rate of 30 MHz. In facing this challenge, the system could take advantage of a fast pre-processing of data on dedicated FPGAs. The results of an R&D on these technologies, developed in the context of the LHCb Upgrade I, are presented in this document. In particular, the details and potential benefits of an approach based on producing in real-time sorted collections of hits in the VELO detector (pre-tracks) are discussed. These pre-processed data can then be used as seeds by the High Level Trigger (HLT) farm to find tracks for the Level 1 trigger with much lower computational effort than possible by starting from the raw detector data, thus freeing an important fraction of the power of the CPU farm for higher level processing tasks.
Highlights
The LHCb detector [1] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks
Reconstruction of tracks in the vertex detector (VELO) is the first step in the HLT1 sequence [2], is a necessity for every tracking sequence considered in the Run 3 plan, and it burns a large fraction of the available time
Cards with the needed features are commercially available today, they have the low-latency response needed to operate within the Event Builder (EB) requirements, and are integrated in the EB by insertion in an available PCIe slot in each EB node connected to the detector of interest
Summary
The LHCb detector [1] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. This system can operate in a pipeline before the events are loaded in the CPU farm that executes the HLT1, freeing up time that can be used, for example, to process tracks with low pT or to run the second stage of the trigger (HLT2). Reconstruction of tracks in the vertex detector (VELO) is the first step in the HLT1 sequence [2], is a necessity for every tracking sequence considered in the Run 3 plan, and it burns a large fraction of the available time For this reason, it is a natural target for offloading to a specialized device.
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