Towards a new generation of Parton Distribution Functions: from high-precision collider data to lattice Quantum Chromodynamics
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Date
27/11/2021Author
Giani, Tommaso
Metadata
Abstract
A precise understanding of the proton structure, encoded in Parton Distribution
Functions (PDFs), is required to make reliable predictions and analyses at the
Large Hadron Collider (LHC), the main source of experimental data probing
subnuclear interactions we have today. PDFs have played a central role in
the recent discovery of the Higgs boson and, since it is increasingly clear that
any effect due to new physics will manifest itself as small deviations from the
current theory, a precise determination of PDFs is likely to be a key ingredient
for new physics studies. The PDFs are formally defined as matrix elements of
renormalized operators in Quantum Chromodynamics (QCD) involving hadronic
states. They are inherently non-perturbative quantities, and they are extracted
from global QCD analysis over experimental data using the so-called factorization
theorems. Producing a new generation of PDFs, satisfying the precision and
reliability requirements demanded by the current research, is a challenging task
which involves, together with the experimental data input, the development
of robust fitting methodologies, along with new physical ideas. In this thesis
we present a number of progresses which have been developed in the last few
years in the context of PDFs determination, some of which will lead to the next
PDFs release by the NNPDF collaboration. In particular we will discuss a new
framework for global PDFs determinations, the impact of new experimental data,
with particular emphasis on jets data, the inclusion of theory uncertainty in a
PDFs fit and the treatment of heavy quarks distributions. We will then discuss a
set of recent ideas which would allow to extract PDFs from equal time correlators
computable within the framework of lattice QCD, and we will present results
regarding data coming from different lattice approaches and collaborations.