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].