3DSPIN performed the first extraction of unpolarized Transverse Momentum Distributions (TMDs) from a fit of all available data. We considered in total more than 8000 data points from sharply different experiments (electron-proton and proton-proton collisions, fixed-target and collider experiments). We demonstrated for the first time that the formalism based on TMDs can reasonably describe this multitude of data points. This work inaugurated the age of global TMD extractions. The extracted TMDs describe the distribution of quarks inside the proton in 3-dimensional momentum space.
DSPIN drastically improved the perturbative accuracy of TMD extractions reaching an unprecedented level (N3LL). We published a new extraction, taking into account only a subset of presently available data, but including in particular several new measurements by LHC experimental collaborations. The theory/data agreement was excellent. To achieve this result, we created a platform of software tools for TMD phenomenology, called NangaParbat, which we made available for public use.
The second goal of 3DSPIN was obtaining from TMDs information on quark Orbital Angular Momentum (OAM). Unfortunately, we have not been able to achieve this goal. The main route we wanted to follow (based on the study of the so-called Sivers function), turned out not to be sufficiently motivated, as we demonstrated in a dedicated publication. The study of the Sivers function per se, however, remained a relevant goal of the project and we obtained a state-of-the-art extraction of this function, which necessarily relied on the knowledge of the unpolarized TMDs. This stands as another milestone achievement of the 3DSPIN project and made it possible to reconstruct the distribution of quarks in momentum space for a transversely polarized nucleon.
Apart from these core achievements, 3DSPIN also obtained the following non-exhaustive list of results:
- a series of studies on the transversity parton distribution function, opening the way to a global fit of this quantity;
- a series of studies on the possibility to access gluon unpolarized and polarized TMDs in future experiments, together with a model calculation of gluon TMDs, which are presently essentially unknown.
- a model calculation of pion TMDs based on the AdS/QCD correspondence principle, including the application of TMD evolution on this calculation, together with other results on the pion structure.
