Uncertainties in NLO + parton shower matched simulations of inclusive jet and dijet production
Stefan Hoeche, Marek Schonherr
TL;DR
This paper quantifies perturbative and non-perturbative uncertainties in MC@NLO matched simulations of inclusive jet and dijet production by comparing SHERPA+BLACKHAT predictions to ATLAS and CMS 7 TeV data. It analyzes scale variations (mu_F, mu_R, mu_Q) and non-perturbative effects from MPI and hadronization, highlighting that resummation-scale uncertainties are dominant in shower-dominated regions while MPI uncertainties matter in underlying-event-dominated regions. The results show generally good agreement across many observables, with notable discrepancies in forward or large-rapidity configurations due to scale choices, and propose NLO matrix-element–parton-shower merging as a path to reduce these uncertainties. The work provides a framework for reliable uncertainty assignment in MC@NLO/POWHEG predictions, informing LHC phenomenology and the interpretation of jet-physics measurements.”
Abstract
We quantify uncertainties in the Monte-Carlo simulation of inclusive and dijet final states, which arise from using the MC@NLO technique for matching next-to-leading order parton level calculations and parton showers. We analyse a large variety of data from early measurements at the LHC. In regions of phase space where Sudakov logarithms dominate over high-energy effects, we observe that the main uncertainty can be ascribed to the free parameters of the parton shower. In complementary regions, the main uncertainty stems from the considerable freedom in the simulation of underlying events.