Elementary Particle Physics

The observation of the scaling properties of the structure functions w and vw of deep inelastic electron 1 2 nucleon scattering [1]+ has been taken by many people as an indication for an approximate scale invariance of the world. It was pointed out by Wilson [2], that in many field theories it is possible to assign a dimension d to every fundamental field, which proves to be a conserved quantum number as far as the most singular term of an operator product expansion at small distances ((x-y) +a) is con- JJ cerned++. Later it was shown, at the canonical level, that in many field theories the dimension of a field seems to be a c:pod quantum number even in the terms less singular at small (x-y) , as long as they all belong to the strongest l light cone singularity (i. e. (x-y)2+a) [3]. The assumption that this type of scale invariance on the light cone be present in the operator product ex­ pansion of two electromagnetic currents has provided us with a rather natural explanation of the observed scaling phenomena. We should like to mention, however, that this ex­ planation cannot account for the precocity with which scaling is being observed experimentally in energy regions, in which resonances still provide prominent contributions to the final states [4].