Speaker
Description
We investigate the impact of recently computed N3LO corrections to QCD splitting and deep-inelastic scattering (DIS) coefficient functions on fits of parton distribution functions (PDFs) using the xFitter framework. By comparing fits performed at different perturbative orders, we analyze the resulting modifications to the PDFs and their associated uncertainties, incorporating correlated experimental errors. The results demonstrate the importance of N3LO corrections and highlight the need for further theoretical refinement in the low-x regime. Furthermore, we study the impact of resummation-scale variations on the splitting functions and on the strong coupling constant $\alpha_{s}$. These variations introduce a significant additional uncertainty in the PDFs that has not been considered previously. We study the impact of this uncertainty on fits of HERA DIS data and its implications for predictions of top quark pair production at the LHC.