Details

Autor(en) / Beteiligte

• McGowan, J
• Cridge, T
• Harland-Lang, L. A
• Thorne, R. S

Titel

Approximate N[Formula omitted]LO parton distribution functions with theoretical uncertainties: MSHT20aN[Formula omitted]LO PDFs

Ist Teil von

• The European physical journal. C, Particles and fields, 2023-03, Vol.83 (3)

Ort / Verlag

Springer

Erscheinungsjahr

2023

Link zum Volltext

Quelle

SpringerLink (Online service)

Beschreibungen/Notizen

• We present the first global analysis of parton distribution functions (PDFs) at approximate N [Formula omitted]LO in the strong coupling constant [Formula omitted], extending beyond the current highest NNLO achieved in PDF fits. To achieve this, we present a general formalism for the inclusion of theoretical uncertainties associated with the perturbative expansion in the strong coupling. We demonstrate how using the currently available knowledge surrounding the next highest order (N [Formula omitted]LO) in [Formula omitted] can provide consistent, justifiable and explainable approximate N [Formula omitted]LO (aN [Formula omitted]LO) PDFs. This includes estimates for uncertainties due the currently unknown N [Formula omitted]LO ingredients, but also implicitly some missing higher order uncertainties (MHOUs) beyond these. Specifically, we approximate the splitting functions, transition matrix elements, coefficient functions and K-factors for multiple processes to N [Formula omitted]LO. Crucially, these are constrained to be consistent with the wide range of already available information about N [Formula omitted]LO to match the complete result at this order as accurately as possible. Using this approach we perform a fully consistent approximate N [Formula omitted]LO global fit within the MSHT framework. This relies on an expansion of the Hessian procedure used in previous MSHT fits to allow for sources of theoretical uncertainties. These are included as nuisance parameters in a global fit, controlled by knowledge and intuition based prior distributions. We analyse the differences between our aN [Formula omitted]LO PDFs and the standard NNLO PDF set, and study the impact of using aN [Formula omitted]LO PDFs on the LHC production of a Higgs boson at this order. Finally, we provide guidelines on how these PDFs should be used in phenomenological investigations.