I will discuss a view on the issues of describing unpolarised SIDIS data in their entire spectrum, as well as possible solutions.
Fragmentation functions, describing the formation of hadrons from partons, are an indispensable tool in the interpretation of hadron-production data, e.g., in the investigation of nucleon structure via semi-inclusive deep-inelastic scattering. The cleanest process to access fragmentation functions is hadron production in electron-positron annihilation. In this review a selection of recent...
We discuss how recent data from the Belle Collaboration on transverse $\Lambda$ polarisation measured in $e^+e^-$ annihilation processes could be used to extract, for the first time, the polarising fragmentation function. This, giving the probability that an unpolarised parton fragments into a transversely polarised spin-1/2 hadron, represents one of the 8 leading-twist transverse momentum...
Describing qT-dependent SIDIS distributions requires consideration of two different regimes which involve two different factorization schemes. In both cases, the necessary ingredients include parton distribution and fragmentation functions (PDFs and FF), which are traditionally extracted in statistical analyses with collinear observables. In this talk I will present examples of how the errors...
The Drell-Yan process and electron-positron annihilation offer a natural arena for studies of non-collinearity. We [1] show how covariantly defined variables for these processes and also for semi-inclusive deep inelastic scattering are suited to get a feeling for the magnitude of intrinsic tranverse momenta.
[1] P.J. Mulders and C. Van Hulse ArXiv:1903.11467 [hep-ph]
Transverse Momentum Dependent (TMD) parton distributions obtained from the Parton Branching (PB) method are combined with next-to-leading-order (NLO) calculations of Drell-Yan (DY) production. We apply the MC-at-NLO method for the hard process calculation and matching with the PB TMDs. We compute predictions for the transverse momentum, rapidity and phi-* spectra of Z bosons. We find that...
The process e + p -> e + J/psi + jet + X, where the proton can be polarized, is computed in the transverse momentum-dependent (TMD) factorization framework. This framework is applicable in the regime where the J/psi - jet pair is produced almost back-to-back in the transverse plane, such that its total transverse momentum is a measure of the primordial k_t of the parton. We show that in the...
We calculate the cos 2φ asymmetry in J/ψ production in electron-proton collision for the kinematics
of the planned electron-ion collider (EIC). This directly probes the Weisz¨acker-Williams (WW) type
linearly polarized gluon distribution. Assuming generalized factorization, we calculate the asymmetry
at next-to-leading-order (NLO) when the energy fraction of the J/ψ satisfies z < 1 and the...
In the last years a big progress has been made in the quark sector of TMDs, but the gluon sector is so far much less developed, due to the difficulty to cleanly probe gluons in high-energy processes.
A very promising way to access them, but also challenging, is through quarkonia production. However, a solid theoretical framework is still lacking.
In this talk I will present new developments...
Among the eight leading twist gluon TMDs, gluon Sivers function (GSF) has been the limelight in hadron physics. GSF is not yet known fully, though attempts have been made. The $J/\psi$ production has been advertised to probe the gluon TMDs. In this talk, we present the calculation of single-spin asymmetry (SSA) in $pp^\uparrow\to J/\psi+X$ process to probe the unknown GSF within the...
While significant steps toward the formal definition of quark TMDs and their extraction from experimental data through global fits has been made in the last years, the gluon-TMD field represents a largely unexplored territory. Pursuing the goal of extendending our knowledge of this sector, we present analytic expressions for all $T$-even gluon TMDs at twist-2, calculated in a spectator model...
ALICE is the experiment specifically designed for the study of the Quark-Gluon Plasma (QGP) in heavy-ion collisions at the CERN LHC. Heavy-ion collisions help us to understand quarkonium suppression and regeneration mechanisms in the presence of the QGP. However, a modification of heavy quarkonium production can also take place in proton-nucleus collisions, where a QGP is not expected to be...
Fixed-target pp and pA collisions with a proton beam at the TeV scale provide unique laboratories for the study of the nucleon’s internal dynamics and, more in general, for the investigation of the complex phenomena arising in the non-perturbative regime of QCD. Due to the substantial boost of the reaction products in the laboratory frame, fixed-target collisions allow to access the poorly...
