COMPOSITE WEAK BOSONS

Dynamical mechanism of composite Wand Z is studied in a lIN field theory model with four-fermion interactions in which glohal weak SU(2} symmetry is broken explicitly by electromagnetic interaction.Issues involved in such a model are discussed in detail.Ueviation from gauge coupling due to compositeness and higher order loop corrections are examined to show that this class of models are consistent not only theoretically but also experimentally. I NTROIlUCT IONGauge bosons have a nice geometrical interpretation for their existence.In the standard picture, weak bosons are gauge bosons which acquire mass by spontaneous symmetry breakdown.Experimentally, the most persuasive evidence for this picture is the relation between the weak boson masses and the weak mixing angle.As was emphasized by Hung and Sakurai l } and by Bjorken 2 ), however, such a relation can be naturally realized at a phenomenological level even if Wand Z are not gauge bosons.A conclusive test must probe the couplings among W, Z and photon in future experiment.From a theoretical viewpoint, renormalizability of the spontaneously broken theory guarantees approximate validity of tree-diagram predictions except for Jliggs bosons masses.Elementary lliggs bosons are, until now, an artifice which mars the otherwise beautiful standard theory.By contrast, if Wand Z are composite and much lighter than their constituents, they behave just like gauge bosons and lIiggs bosons are not needed.There is a long history in construction of gauge-like bosons as composites of fermion-anti-