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QWORK Sintesi della relazione

Project ID: 320389
Finanziato nell'ambito di: FP7-IDEAS-ERC
Paese: Netherlands

Mid-Term Report Summary - QWORK (Quantum Chromodynamics at Work)

(7) Summary of ERC Advanced Grant Project: Quantum Chromodynamics at Work (QWORK), project no. 320389

The basic aim of the proposal is to go beyond the collinear approximation for partons in high-energy processes. The collinear dominance is imposed by the kinematics. The transverse momentum dependence (TMD) is an intrinsic part of the nonperturbative partonic structure of the nucleons but cannot be decoupled from the dynamics governed by the interactions in Quantum Chromodynamics (QCD). In the first half of the project considerable progress towards the objectives in the project have been made. These were the better understanding of the transverse momentum dependence in the partonic structure, which was made easier by exploiting the rank expansion in tensors built from the transverse momentum vectors. For the corresponding functions the azimuthal dependence is separated from the dependence on transverse momentum squared, which leads to an improved understanding of the operator structure, incorporating all time-reversal odd effects that are responsible for the process dependence in TMD physics. In the theoretical studies the effects have been linked to the evolution of TMD functions using also methods from soft collinear effective theories and the studies have been linked to multiparton interactions.
Also towards the second objective progress was made. This involves the phenomenology and the investigations of the importance of novel partonic correlations in high energy processes at existing accelerators (e.g. RHIC/Brookhaven or LHC/CERN). Theoretical insights were immediately translated into possible new experimental handles to an improved understanding of transverse momentum dependence in specific processes, in particular processes initiated by the collisions of hadrons such as at Brookhaven (in that case with polarization) or at CERN. Even if the protons are unpolarized one may have effects because linear polarization of gluons may be correlated with their transverse momentum.

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