SU(2) ⊗ U(1) ⊗ U(1)′ weak-interaction model andΔI=12enhancement

The $\Delta I=\frac{1}{2}$ enhancement in nonleptonic decays is achieved in an SU(2) ⊗ U(1) ⊗ U(1)′ model by the role of an additional neutral gauge boson, $X_{\mu }$. The new vector boson couples to the hadronic neutral current that has predominantly isoscalar $\Delta S=0\mathrm{}$ term plus a small $\Delta S\ne 0$ term but it does not interact with leptons. The associated $\Delta S=2\mathrm{}$ processes can be made small under due conditions on parameters. Several manifestations of $X_{\mu }$ as a gauge boson or gluon bound state are speculated.