Contribution plenary talk
A peek into quark confinement: transverse polarized scattering and quark-gluon correlations in nucleons (2018 GHP APS fellow)
Why quarks cannot be separated far enough to be observed in isolation remains a major unresolved question in hadronic structure: What are the types and strengths of the interactions that keep the colorful, asymptotically free, partons of short distance, high energy perturbative QCD confined inside colorless entities like mesons and baryons? One step towards the answer is the study of quark-gluon ($qg$) correlations, a process described as having twist-3, by using inclusive scattering of polarized lepton beams on nucleons with spins aligned transversely to the lepton helicity. Transverse double polarized scattering provides direct access to twist-3, which represents $qg$ correlations, the simplest form of partonic interaction beyond scale corrections. In this talk I will review the experimental study of nucleon spin structure with transverse polarization at SLAC and JLab over a 25 years period, with conclusive results of non-zero twist-3 processes, providing a quantitative glimpse into one type of mechanism that can help in understanding why quarks cannot escape hadrons.