Influence of additional fermions and gauge bosons on Re( ϵ′/ ϵ)

Abstract

The CP-violation parameter Re( ϵ′/ ϵ) has previously been calculated in the standard model and the result depends on the top quark mass m t in an exciting way. We consider how the result is modified in two specific extensions of the standard model. The first adds only fermions, an extra vector-like quark doublet, and tends to reduce Re(ϵ′/ϵ). The second contains three extended fermion families with the third family treated differently and additional gauge bosons, in the 331 model, and can accommodate larger values of Re( ϵ′/ ϵ) for a given m t. When the experimental values of m t and Re( ϵ′/ ϵ) are known more accurately, it will allow discrimination between theories. If the lower experimental number Re( ϵ′/ ϵ) = (0.74±0.60) × 10 −3 (Fermilab, E731) is confirmed and m t is near the expected value the standard model is acceptable. But, if the higher value Re(ϵ′/ϵ) = (2.3±0.65) × 10 −3 (CERN, NA31) persists and m t is around 150 GeV, a dynamics like the 331 model which treats the third family differently from the first two and contains additional gauge bosons seems to be favored.