Strategies for Modeling Extreme Luminosities in the CMS Simulation

The LHC simulation frameworks are already confronting the High Luminosity LHC (HL-LHC) era. In order to design and evaluate the performance of the HL-LHC detector upgrades, realistic simulations of the future detectors and the extreme luminosity conditions they may encounter have to be simulated now. The use of many individual minimum-bias interactions to model the pileup poses several challenges to the CMS Simulation framework, including huge memory consumption, increased computation time, and the necessary handling of large numbers of event files during Monte Carlo production. Simulating a single hard scatter at an instantaneous luminosity corresponding to 200 pileup interactions per crossing can involve the input of thousands of individual minimum-bias events. Brute-force Monte Carlo production requires the overlay of these events for each hard-scatter event simulated.