O 4 symmetry, light-cone expansion and the electroproduction structure function

Abstract

The electroproduction structure function is examined by formulating the method of the light-cone expansion via theO4 symmetry advocated by Nachtman. The hadron matrix elements of the expansion operators are expressed in terms of theO4 spherical harmonics. The structure functions, for the elementary and composite particles the wave functions of which are given by the Bethe-Salpeter amplitudes, are studied by taking account of the dynamical effects for the superrenormalizable and renormalizable interacting spinless particles. For the composite particles, by considering the high-rank behaviour of the matrix elements, it is shown that the Drell-Yan-West threshold relation holds for the renormalizable interaction if the anomalous dimension is neglected. In the case of the superrenormalizable theory, the relation holds exactly. There exist possible Regge poles in the complex angular-momentum plane ofO4 symmetry for the matrix elements due to the Regge behaviour in the scattering process for the constituent particles. In the case of the superrenormalizable theory, we get the Regge behaviour for the structure function, but, for the renormalizable theory, the structure function may inevitably have the non-Regge behaviour indicated by De Rujulaet al.