### Andrea Signori

Jefferson Lab
###
Transverse paths to an EIC and beyond

Transverse-momentum-dependent distributions (TMDs) provide a description
of hadron structure and hadronization in 3D momentum space in terms of
quarks and gluons, the elementary degrees of freedom of QCD. As such,
they are among the nonperturbative links between hadrons and elementary
particles. At variance with the collinear one-dimensional distribution and
fragmentation functions, TMDs take into account the spin-momentum
correlations between the hadron and its elementary constituents and are
thus more rich and informative.

We know how to define the TMDs by means of operators in QCD.
Nonetheless, there are many nontrivial open questions concerning the
TMDs. For example, their emergence from factorization theorems in hard
scattering processes, their universality properties, their functional
form at low transverse momentum, and its flavor dependence.
Over the past years, thanks to a fruitful synergy of theoretical and
experimental investigations, we have made significant progress in the
study of TMDs and hadron structure in 3D momentum space, but we are
still far from a complete understanding.

In this talk I will review theoretical and phenomenological aspects of
TMDs, connecting the physics programs of Jefferson Lab and the LHC, and
stressing the relevance of an Electron-Ion Collider for improving our
quantitative understanding of hadron structure.

Back to the Theory seminar page.