Gluon and Wilson loop TMDs for hadrons of spin ≤ 1
Daniël Boer (Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Nijenborgh 4, NL-9747 AG, Groningen, The Netherlands); Sabrina Cotogno (Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV, Amsterdam, The Netherlands, Nikhef, Science Park 105, NL-1098 XG, Amsterdam, The Netherlands); Tom Daal (Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV, Amsterdam, The Netherlands, Nikhef, Science Park 105, NL-1098 XG, Amsterdam, The Netherlands); Piet Mulders (Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV, Amsterdam, The Netherlands, Nikhef, Science Park 105, NL-1098 XG, Amsterdam, The Netherlands); Andrea Signori (Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV, Amsterdam, The Netherlands, Nikhef, Science Park 105, NL-1098 XG, Amsterdam, The Netherlands); et al - Show all 6 authors
In this paper we consider the parametrizations of gluon transverse momentum dependent (TMD) correlators in terms of TMD parton distribution functions (PDFs). These functions, referred to as TMDs, are defined as the Fourier transforms of hadronic matrix elements of nonlocal combinations of gluon fields. The nonlocality is bridged by gauge links, which have characteristic paths (future or past pointing), giving rise to a process dependence that breaks universality. For gluons, the specific correlator with one future and one past pointing gauge link is, in the limit of small x , related to a correlator of a single Wilson loop. We present the parametrization of Wilson loop correlators in terms of Wilson loop TMDs and discuss the relation between these functions and the small- x ‘dipole’ gluon TMDs. This analysis shows which gluon TMDs are leading or suppressed in the small- x limit. We discuss hadronic targets that are unpolarized, vector polarized (relevant for spin-1 / 2 and spin-1 hadrons), and tensor polarized (relevant for spin-1 hadrons). The latter are of interest for studies with a future Electron-Ion Collider with polarized deuterons.
