Parity non-conservation in the pp system at low energy: Critical remarks about direct quark approaches

Several papers dealing with predictions for the parity-non-conserving longitudinal asymmetry in pp scattering at low energy, using either a quark-model approach or the concept of parity admixture of vector mesons, are reviewed. About 10 papers which are concerned with the determination of the sign are discussed here. It is shown that they predict a sign for the asymmetry which is likely to be incorrect and, in any case, in contradiction with the standard theoretical understanding of the sign actually determined by experiment. The relationship of these approaches with that based on the old factorization approximation is emphasized. In this order, many details are given, and obviously special attention is given to the sign prediction (conventions, definitions, phases, etc.). ((orig.))