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

Abstract

The LHCb experiment is a forward spectrometer, designed to study beauty and charm quarks Physics at the 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 paper, 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 ~ 30 MHz full event-rate. In particular, this paper 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.