  The LHC trigger and data acquisition systems will need significant
modifications to operate at the HL-LHC. Due to the increased occupancy of each
crossing, Level-1 trigger systems would experience degraded performance of the
LHC algorithms presently selecting up to 100 kHz of crossings from the LHC
input rate of 40 MHz. The DAQ systems will experience larger event sizes due to
greater occupancy and higher channel counts of new detectors. This paper
summarizes findings and recommendations to upgrade the LHC experiments trigger
and data acquisition systems for operation at the HL-HLC.
