Supertwistors, massive superparticles and κ-symmetry

We consider a D = 4 two-twistor lagrangian for a massive particle that incorporates the mass-shell condition in an algebraic way, and extend it to a two-supertwistor model with N = 2 supersymmetry and central charge identified with the mass. In the purely supertwistorial picture the two D = 4 super twistors are coupled through a Wess-Zumino term in their fermionic sector. We demonstrate how the ?-gauge symmetry appears in the purely supertwistorial formulation and reduces by half the fermionic degrees of freedom of the two supertwistors; a formulation of the model in terms of ?-invariant degrees of freedom is also obtained. We show that the ?-invariant supertwistor coordinates can be obtained by dimensional (D = 6 ? D = 4) reduction from a D = 6 supertwistor. We derive as well by 6 ? 4 reduction the N = 2 D = 4 massive superparticle model with Wess-Zumino term introduced in 1982. Finally, we comment on general superparticle models constructed with more than two supertwistors.