Unification of twistors and Ramond vectors

We generalize the idea of supertwistors and introduce a new supersymmetric object - the $\theta$-twistor which includes the composite Ramond vector [11] well known from the spinning string dynamics. The symmetries of the chiral $\theta$-twistor superspace are studied. It is shown that the chiral spin structure introduced by the $\theta$-twistor breaks the superconformal boost symmetry but preserves the scale symmetry and the super-Poincare symmetry. This geometrical effect of breaking correlates with the Gross-Wess effect of the conformal boost breaking for bosonic scattering amplitudes.