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.
The Large Hadron Collider will commence operations in the latter half of 2008. The plans of the LHC experiments ALICE, ATLAS, CMS and LHCb are described. The scenario for progression of luminosity and the strategies of these 4 experiments to use the
initial data are detailed. There are significant measurements possible with integrated luminosities of 1, 10 and 100 pb^-1. These measurements will provide essential calibration and tests of the detectors, understanding of the Standard Model backgrounds and a first oportunity to look for new physics.
