SUPERTWISTOR FORMULATION OF THE SPINNING PARTICLE

It is shown that, like the (spacetime-supersymmetric) superparticle action, the (worldline-supersymmetric) spinning particle action can, for spacetime dimensions d = 3, 4, be expressed in terms of the components of a supertwistor. For d = 3 the supertwistor forms of the superparticle and spinning particle actions are identical (for positive energy); for d = 4 they have differing "spin-shell" constraints which lead to distinct quantum theories, although the two actions are shown to be classically equivalent on reduction to physical degrees of freedom. Similar results are obtained for d = 6, 10 by dimensional reduction to d = 4.