Exact NNLO corrections vs K-factors in PDF fits

Parton distribution functions (PDFs) often include datasets corresponding to processes whereby the theoretical predictions at next-to-next-to-leading order (NNLO) in peturbative QCD have to be approximated, and this approximation may be performed using K-factors, which in turn depend on the PDF set used to compute them. In this study, we investigate the impact of K-factors produced with various PDF sets, namely CT18, MSHT20 and NNPDF4.0 on (differential) cross sections of top pair production at the Large Hadron Collider (LHC). Furthermore, we perform a new fit (otherwise analogous to NNPDF4.0 with MHOUs) where the exact NNLO corrections are used in the fitting procedure and compare the K-factors obtained from this fit with those obtained from the above mentioned PDF sets. We find good agreement amongst K-factors obtained from these different PDF sets.