Fast readout and performance of the upgraded HADES RICH in heavy ion collisions

The HADES Experiment (High Acceptance DiLepton Spectrometer) aims to measure baryonic matter at high densities but moderate fireball temperatures using heavy ion collisions. In a recent Ag$+$Ag beamtime, at an incident energy of $1.58$ A GeV, $15.268\times {10}^9$ events have been collected at triggered event rates of 16–18 kHz. The data were recorded with the upgraded RICH detector, including the newly developed DiRICH readout chain and using HAMAMATSU H12700 MAPMTs as photon detector. In this article, we demonstrate the success of this upgrade and present first result on timing precision of the full HADES RICH detector.