Scientific Topics
The study of the quark-gluon structure of nucleons and nuclei is one of the main goals of modern physics.
From one side transverse space distributions of partons, encoded in Generalized Parton Distributions (GPDs),
and transverse momentum dependent distributions, encoded in Transverse Momentum Distributions (TMDs),
have been widely recognized as key objectives of the JLab 12 GeV upgrade and a driving force behind construction of the Electron Ion Collider.
On the other side, the knowledge of the structure of the proton, and in particular of TMDs, is relevant for studies in proton colliders, even at the LHC energies.
The transverse momentum dynamics may be very important at low x. It is manifested in very high energy hadronic collisions and is described by Unintegrated Gluon Distribution Functions. For example, the transverse-momentum spectrum of vector bosons produced in Drell-Yan-like processes at the LHC is influenced by the contribution of intrinsic partonic transverse momentum.
Higgs production is influenced by gluon TMDs and is also sensitive to linear gluon polarization. LHC data can offer unique insights to improve the knowledge of TMDs and, on the contrary, the knowledge of TMDs can be necessary to achieve high-precision results demanded by the search for new physics.
TMDs can also be affected by the nuclear environment in heavy-ion collisions, leading to the concept of Nuclear TMDs.
In recent years the measurements of single spin asymmetries (SSAs) in final state hadrons and photons in semi-inclusive and exclusive processes have been widely used to access the underlying GPDs and TMDs.
Although the interest to TMD/PDF has grown enormously, we are still in need of fresh theoretical and phenomenological ideas. The 2016 marks the 20 years since first measurements of SSAs were performed by HERMES collaboration and one of the main challenges still remaining is the extraction of actual 3D PDFs (GPDs and TMDs) from different spin and azimuthal asymmetries in a reliable and model independent way.
We specifically focus on the GPD and TMD programs in particular the question how to extract underlying 3D parton distribution and fragmentation functions from the wealth of data expected from semi-inclusive deep inelastic scattering (SIDIS), pp and e+e- experiments including the future electron-ion collider (EIC), outlining what measurements with present and future facilities are crucial to establish the underlying dynamics defining the nucleon structure across the wide range in Bjorken-x.
Key personalities of the field will contribute to the development of a common research programs and unified treatments of some of the crucial problems in the theory of strong interaction involving 3D PDF and low-x communities, thereby increasing the international support for a multifaceted effort to study the fundamental 3D structure of matter.
