Unification of twistors and Ramond vectors

We generalize the idea of supertwistors and introduce a new supersymmetric object-the θ-twistor which includes the composite Ramond vector [D.V. Volkov, A.A. Zheltukhin, JETP Lett. 48 (1988) 63] well known from the spinning string dynamics. The symmetries of the chiral θ-twistor superspace are studied. It is shown that the chiral spin structure introduced by the θ-twistor breaks the superconformal boost symmetry but preserves the scale symmetry and the super Poincaré symmetry. This geometrical effect of breaking correlates with the Gross-Wess effect of the conformal boost breaking for bosonic scattering amplitudes.