Unitarity mass bounds due to massive spin-1 fields

Summary

If the principle of renormalizability is applied to massive spin-1 fields, then the mechanism of spontaneous symmetry breaking makes a minimal particle content possible. The drawbacks of such a model could possibly be avoided by a duplication of all the states of leptons, quarks and weak bosons. Mass could then be generated without spontaneous symmetry breaking. The couplings of the partner states can be determined by that requirement of renormalizability. Lowest-order processes give rise to upper unitarity bounds on the partner masses. The effect is demonstrated for the decays of the neutrino partner N→W+e or Z+ν. It is shown that unitarity is saved atany partner mass (M) if all orders of perturbation theory are taken into account. The corresponding form factor of the decay amplitude is estimated. It is suppressive atM>m _w/√α so that the specific decay widthΓ/M even decreases with increasingM. The form factor exhibits a substantial imaginary part, which opens up a new approach to the issue ofCP violation.