Design and Commissioning of the First 32-Tbit/s Event-Builder

The large hadron collider beauty (LHCb) experiment is a forward spectrometer, designed to study beauty and charm quarks physics at the large hadron collider (LHC). To exploit of the higher luminosity that will be delivered during Run3, the full experiment needed a substantial upgrade, from the detector to the data acquisition (DAQ) and high level trigger (HLT). In this article, we will focus on the new DAQ system for the LHCb experiment that represents a substantial paradigm shift compared to the previous one, and to similar systems used by similar experiments in the past and present times. To overcome the inefficiencies introduced by a local selection implemented directly with the readout hardware, the Run3 system is designed to perform a full software reconstruction of all the produced events. To achieve this, both the DAQ and the HLT need to process the
$\sim $
30 MHz full event-rate. In particular, this article will introduce the final design of the system; it will provide a focus on the hardware and software design of the event building (EB) and how we integrated technologies designed for the high performance computing (HPC) world — like InfiniBand HDR (200 Gb/s) — into the DAQ system; we will present performance measurements of the full EB system under different operational conditions; and we will provide a feedback from EB operation during the beginning of the data-taking.