A class of “natural” composite models

Abstract

The starting point is the attractive class of composite models where quarks and leptons appear as fermion-scalar bound states ( Fφ). The aim is to resolve the “naturality” problem associated with fundamental scalars without losing the appealing properties of Fφ-type composite models. A systematic construction of such models is given, where the scalar constituents automatically qualify as light dynamical scalars, i.e. as composite (pseudo) Goldstone bosons. A comfortably large class of composite models then results, where all standard “naturality” requirements are satisfied: the quark and lepton masses are kept small through 't Hooft's chiral protection mechanism; the dynamical scalar “constituents” are light and the CP problem of QCD finds an automatic solution. Further characteristics are economy, absence of light exotics, possibility of three generations and elegance of anomaly matching. It is shown that existing attractive models with fundamental scalars can be made “natural” in the sense defined above.