A 4D real-time tracking device for the LHCb Upgrade II

The LHCb experiment will enter the High Luminosity phase during the Run 4 of the LHC. In order to fully exploit the flavour opportunities of the HL-LHC, an upgrade of the detector, the LHCb Upgrade II, will be installed during the LS4 (2030), targeting an instantaneous luminosity of 1-2 10^34 cm^-2 s^-1 and aiming at collecting an integrated luminosity of 300 fb^-1. With the higher luminosity the mean number of interactions at each bunch crossing will increase up to μ ≈ 50, resulting in a significant increase of the total number of tracks per each event, and providing a challenging environment for the track reconstruction, which has to be performed in real time at the visible crossing rate of 30 MHz. The introduction of precise timing detectors will be crucial to mitigate the pile-up effects, allowing the LHCb experiment to exploit larger data samples and keep producing high quality measurements. The author presents a 4D real-time tracking device capable of reconstructing four dimensional particle tracjectories in real time using precise space and time information of the hits, to be applied to a possible Upgrade II of the VELO sub-detector. The proposed fast track finding device is implemented in commercial FPGAs with a modular and highly parallelized and pipelined architecture to work at high rates and with latency below 1 μs. The performance of the 4D fast tracking algorithm and its hardware implementation have been tested on a custom board equipped with latest generation FPGAs (Xilinx Virtex UltraScale) and high input data bandwidth (up to 1.6 Tbps). The demonstrator prototype has been tested with simulated data from a sector (∼ 1/64) of the LHCb VELO and has to be considered as a proof of principle of a large scale system able to process the full detector.