  A twistor model of a free massless spinning particle in 4-dimensional
Minkowski space is studied in terms of spacetime and spinor variables. This
model is specified by a simple action, referred to here as the gauged Shirafuji
action, that consists of twistor variables and gauge fields on the
1-dimensional parameter space. We consider the canonical formalism of the model
by following the Dirac formulation for constrained Hamiltonian systems. In the
subsequent quantization procedure, we obtain a plane-wave solution with
momentum spinors. From this solution and coefficient functions, we construct
positive-frequency and negative-frequency spinor wave functions defined on
complexified Minkowski space. It is shown that the Fourier-Laplace transforms
of the coefficient functions lead to the spinor wave functions expressed as the
Penrose transforms of the corresponding holomorphic functions on twistor space.
We also consider the exponential generating function for the spinor wave
functions and derive a novel representation for each of the spinor wave
functions.
