Accelerating LHC event generation with simplified pilot runs and fast PDFs

Poor computing efficiency of precision event generators for LHC physics has become a bottleneck for Monte-Carlo event simulation campaigns. We provide solutions to this problem by focusing on two major components of general-purpose event generators: The PDF evaluator and the matrix-element generator. For a typical production setup in the ATLAS experiment, we show that the two can consume about 80% of the total runtime. Using NLO simulations of pp -> +t- pound + jets and pp -> t (t)over bar+ jets as an example, we demonstrate that the computing footprint of LHAPDF and SHERPA can be reduced by factors of order 10, while maintaining the formal accuracy of the event sample. The improved codes are made publicly available.

Automated summary

The poor computing efficiency of precision event generators for LHC physics is a bottleneck for Monte-Carlo event simulations. By focusing on the PDF evaluator and matrix-element generator, we have found solutions to reduce the computing footprint while maintaining the accuracy of the event sample.