Decays of the heavy top and new insights on ϵK in a one-VLQ minimal solution to the CKM unitarity problem

Abstract

We propose a minimal extension of the Standard Model where an up-type vector-like quark, denoted T, is introduced and provides a simple solution to the CKM unitarity problem. We adopt the Botella-Chau parametrization in order to extract the 4 × 3 quark mixing matrix which contains the three angles of the 3 × 3 CKM matrix plus three new angles denoted θ, θ, θ. It is assumed that the mixing of T with standard quarks is dominated by θ. Imposing a recently derived, and much more restrictive, upper-bound on the New Physics contributions to ϵ, we find, in the limit of exact θ dominance where the other extra angles vanish, that ϵKNP is too large. However, if one relaxes the exact θ dominance limit, there exists a parameter region, where one may obtain ϵKNP in agreement with experiment while maintaining the novel pattern of T decays with the heavy quark decaying predominantly to the light quarks d and u. We also find a reduction in the decay rate of K→ πνν¯.