Beam splashes seen by the CMS detector in view of the re-starting of the LHC

A "splash" event seen in the CMS detector at the beginning of the restart of the LHC on 22 April 2022. In splash events particles traverse the detector horizontally from one side to the other. The particles in the detector come from beam particles travelling inside the LHC beam pipe which are directed into collimators several meters before the experimental cavern. When particles hit the collimator many muons move through the experiment, leaving signals in the electromagnetic calorimeter and in the hadronic calorimeters.