### Leonard Gamberg

Penn State Berks
###
The 3-D Partonic Structure of the Nucleon

In Quantum Chromodynamics, the theory of the strong interactions, the
nucleon emerges as a relativistic strongly interacting system of quarks
and gluons (partons). QCD factorization theorems provide a reliable
theoretical formalism that enables one to connect hadron observables to
their confined parton degrees of freedom. With the use of collinear
factorization, experiments have provided a well documented
one-dimensional (longitudinal momentum) snapshot of the nucleonâ€™s
internal structure in terms of universal collinear parton distribution
functions.

In more recent years, new data sensitive to the transverse momentum
partonic structure of hadrons are now available worldwide; among them
the COMPASS experiment at CERN (from the earlier HERMES experiment at
DESY), RHIC at BNL, Drell-Yan experiments at Fermi Lab, and SIDIS
experiments at JLAB. In turn, theoretical advances enabled a paradigm
shift in our picture of the partonic structure of the nucleon, which is
now three dimensional in momentum space (or one dimension longitudinal,
and 2 Fourier spatial degrees of freedom). This more detailed structure
is encoded in the transverse momentum dependent parton distribution
functions (TMD PDFs). I will present new work that relates TMD and
collinear QCD factorization in a generalized framework. This work is
preformed in the spirit of providing a quantitative link between
measurements and the 3-D partonic structure of the nucleon.

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