Renormalization group and the deep structure of the proton

The spirit of the renormalization group approach lies entirely in the observation that in a specific theory the renormalized constants such as the couplings, the masses, are arbitrary mathematical parameters which can be varied by changing arbitrarily the renormalization prescription. Given a scale of mass mu , prescriptions can be chosen by doing subtractions of the relevant amplitudes at the continuously varying points mu e/sup t/, t being an arbitrary real parameter. A representation of such a renormalization group transformation mu to mu + mu e/sup t/ is the transformation g to g(t) of the renormalized coupling into a continuously varying coupling constant, the so-called 'running coupling constant'. If, for the theory under investigation there exists a domain of the t space where g(t) is small, then because it is not known how to handle field theory beyond the perturbative approach attention must be focused on the experimental range in which the g(t) 'runs' with small values. The introduction of couplings varying with energy momentum is the major outcome of the renormalization group formalism. Applicability of naive perturbation expansion to non-Abelian gauge theories of strong interactions in the domain of high energy momentum transfer is one result from the renormalization group way of looking at these problems and will probably remain its only use. The author studies deep inelastic scattering of lepton off hadrons, using the light cone operator product expansion. Generalities on the factorization procedure are mentioned. (804 refs).