  We assess the impact of top quark production at the LHC on global analyses of
parton distributions (PDFs) and of Wilson coefficients in the SMEFT, both
separately and in the framework of a joint interpretation. We consider the
broadest top quark dataset to date containing all available measurements based
on the full Run II luminosity. First, we determine the constraints that this
dataset provides on the large-x gluon PDF and study its consistency with other
gluon-sensitive measurements. Second, we carry out a SMEFT interpretation of
the same dataset using state-of-the-art SM and EFT theory calculations,
resulting in bounds on 25 Wilson coefficients modifying top quark interactions.
Subsequently, we integrate the two analyses within the SIMUnet approach to
realise a simultaneous determination of the SMEFT PDFs and the EFT coefficients
and identify regions in the parameter space where their interplay is most
phenomenologically relevant. We also demonstrate how to separate eventual BSM
signals from QCD effects in the interpretation of top quark measurements at the
LHC.
