Parton model description of quark and antiquark correlators and TMDs

Model studies play an important role for the understanding and elucidation of the nonperturbative properties of transverse momentum dependent parton distribution functions (TMDs). The parton model is often a helpful framework and starting point for first explorations of TMD properties and the description of deep-inelastic processes in which TMDs can be accessed. Based on a systematic exploration of the parton model concept, we reconcile the claims in literature that there are 2 independent structures in the quark correlator in the parton model vs the claim that there are 3, and explain the underlying assumptions leading to the different conclusions. We also systematically explore the antiquark correlator and, to the best of our knowledge, for the first time derive the model expressions for all T-even leading and subleading antiquark TMDs. We demonstrate the consistency of the framework which can be generalized in future studies for more sophisticated TMD modelling.