Uncertainties of Sudakov form factors
Stefan Gieseke
TL;DR
The paper quantifies how uncertainties in Sudakov form factors affect spacelike initial-state parton showers in Monte Carlo event generators. It methodically evaluates PDF-related uncertainties (MRST2001/CTEQ6) and variations in the strong coupling scale and parametrizations, using Herwig++ conventions and LHAPDF error sets. The main finding is that α_S scale variations typically dominate, but PDFs can become significant for gluon- and sea-quark–driven branchings at extreme x values, with MRST and CTEQ giving broadly compatible results. These insights inform tuning and uncertainty assessment in parton shower algorithms for improved collider predictions.
Abstract
We study the uncertainties of Sudakov form factors as the basis for parton shower evolution in Monte Carlo event generators. We discuss the particular cases of systematic uncertainties of parton distribution functions and scale uncertainties.