Trigger-less readout architecture for the upgrade of the LHCb experiment at CERN

The LHCb experiment has proposed an upgrade of its detector in order to collect data at ten times its initial design luminosity. The current readout architecture will be upgraded by removing the existing first-level hardware trigger whose efficiency is limited for hadronic channels at high luminosity. The new readout system will record every LHC bunch crossing and send data to a trigger selection process performed entirely by software running in a computing farm. Therefore, the new readout system must cope with higher sub-detector occupancies, higher rate and higher network load. In this paper, we describe the architecture, functionalities and technological challenges of such an upgraded system.