Gauge model with lightWandZbosons

Abstract

We show how the standard electroweak gauge model can be naturally generalized to SU(2) × U(1) × SU(2)', which has twice the number of gauge bosons of the standard model. All known fermions transform with respect to SU(2) × U(1); spontaneous symmetry breaking is achieved with a scalar quartet which links SU(2) and SU(2)' and the usual scalar doublet. The interaction Hamiltonian at low energy reproduces the low-energy phenomenology of the standard model. The high-energy predictions of the model are explored. One $W$ and one $Z$ are less massive than the corresponding bosons of the standard model. These light bosons are relatively narrow, with total widths typically 50 MeV. Cross sections for light $Z$ and $W$ production in $e^{+}{e}^{-}$ collisions and hadron collisions are given. A $Z$ mass as low as 32 GeV is compatible with existing measurements; the most stringent present limit is set by the $e^{+}{e}^{-}$ annihilation cross section.