Simulation of vector boson plus many jet final states at the high luminosity LHC

Abstract

We present a novel event generation framework for the efficient simulation of vector boson plus multi-jet backgrounds at the high-luminosity LHC and at possible future hadron colliders. MPI parallelization of parton-level and particle-level event generation and storage of parton-level event information using the HDF5 data format allow us to obtain leading-order merged Monte-Carlo predictions with up to nine jets in the final state. The parton-level event samples generated in this manner correspond to an integrated luminosity of 3ab −1 and are made publicly available for future phenomenological studies.

Phase space sampling and inference from weighted events with autoregressive flows

“…In many cases, the bottleneck of importance sampling is not necessarily the likelihood evaluation, but rather the small unweighting efficiency achieved by commonly-used techniques [106]. We thus explore the capability of the normalizing flow to be trained on events generated by VEGAS before unweighting.…”

Challenges in Monte Carlo Event Generator Software for High-Luminosity LHC

“…A lot of work has also been done in recent years to implement and benchmark MPI-based workflows on HPC systems. For instance, the Sherpa LO-based generation of merged many-jet samples has been successfully tested [202] on the Cori [203] system at NERSC, both on traditional Intel Haswell CPUs and on many-core Intel KNL CPUs. This work has used a technique similar to that previously developed [204] for testing and benchmarking the scaling of the parallel execution of Alpgen on Mira [205] at ALCF, a supercomputer based on IBM PowerPC CPUs.…”

Exploring phase space with Neural Importance Sampling

“…Typically the sampling performance deteriorates significantly with the phase space dimensionality, i.e. particle multiplicity [15], and the complexity of the integrand. In particular the appearance of intermediate resonances, regularised singularities or quantum-interference effects complicate the situation.…”