PARTON DISTRIBUTION FUNCTIONS WITH PERCENT LEVEL PRECISION

This thesis is dedicated to the construction and applications of
Parton Distribution Functions (PDFs), which are precise enough that
are suitable for comparison with high-precision collider data from
the LHC. We first review the theoretical framework and explain how
PDFs should be used in practice, presenting tools that allow to
seemingly convert between different representations of PDF
uncertainties. We then discuss how these tools are used to construct
the PDF4LHC15 combined sets, which implement the recommendation of
the PDF4LHC group, and provide detailed benchmarks of each of the
combined sets. We describe NNPDF 3.1, the first global PDF analysis
to provide percent level uncertainties for many relevant observables
while being validated by a closure test, with particular emphasis to
the issues that appeared during its preparation and the resources
used solve them.
Finally we present a determination of the strong coupling constant
based on the global NNPDF3.1 fit. We use a new methodology that
correctly propagates all the uncertainties from the PDFs to the
result.