  New sets of CMS underlying-event parameters ("tunes") are presented for the
PYTHIA8 event generator. These tunes use the NNPDF3.1 parton distribution
functions (PDFs) at leading (LO), next-to-leading (NLO), or
next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics,
and the strong coupling evolution at LO or NLO. Measurements of
charged-particle multiplicity and transverse momentum densities at various
hadron collision energies are fit simultaneously to determine the parameters of
the tunes. Comparisons of the predictions of the new tunes are provided for
observables sensitive to the event shapes at LEP, global underlying event, soft
multiparton interactions, and double-parton scattering contributions. In
addition, comparisons are made for observables measured in various specific
processes, such as multijet, Drell-Yan, and top quark-antiquark pair production
including jet substructure observables. The simulation of the underlying event
provided by the new tunes is interfaced to a higher-order matrix-element
calculation. For the first time, predictions from PYTHIA8 obtained with tunes
based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and
underlying-event data with a similar level of agreement to predictions from
tunes using LO PDF sets.
