The structure of the proton at approximate N3LO order: MSHT20aN3LO PDFs

Lucian Harland-Lang (UCL)

Tuesday, 11 October 2022 at 14:30


As we move towards the era of high-luminosity LHC running, the precision in data and theory has reached an unprecedented level. As such an accurate and precise determination of proton structure, as encoded in parton distribution functions (PDFs), is an essential element of the LHC physics programme. An important aspect of PDF fitting that has recently received a great deal of attention is the question of how to correctly account for uncertainties due to missing higher orders in the perturbative calculation of observables that enter the PDF fit.

In this talk I will present the results of a new study in this direction, namely the first global PDF fit at approximate N3LO order in the strong coupling. This applies a general formalism for the inclusion of theoretical uncertainties from missing higher orders into a PDF fit. I will demonstrate how using the currently available knowledge about N3LO theory, an order above the standard NNLO used in current PDF fits, can provide consistent, justifiable and explainable estimates for missing higher order uncertainties. Using this approach I will present the first approximate N3LO PDF fit with theoretical uncertainties, and analyse the differences between these N3LO PDFs and the standard NNLO PDFs.

Slides (PDF, 43 MB)