Measuring nucleon spin and mass through higher twist generalized parton distributions*

Understanding the origin of the proton spin and mass as they emerge from quark and gluon distributions is a central question in QCD and a main quest for current experimental  programs worldwide, as well as at the future Electron Ion Collider (EIC). I will present the essential steps of our approach, involving QCD manipulations of the relevant correlations functions using the equations of motion, to obtain the quark longitudinal angular momentum decomposition into its spin and orbital components. The power of this approach is in that it provides a connection between twist three generalized parton distributions (GPDs) and generalized transverse momentum distributions (GTMDs) while conserving gauge invariance, thus revealing the inner workings of quark and gluon transverse momentum components. I will show how transverse angular momentum can also be described, and the twist three GPD that describes the transverse OAM can be identified. I will finally discuss the extension of this approach to the proton mass decomposition.