Decays of the Heavy Top and New Insights on $ε_K$ 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 14 , θ 24 , θ 34 . It is assumed that the mixing of T with standard quarks is dominated by θ 14 .Imposing a recently derived, and much more restrictive, upper-bound on the New Physics contributions to ε K , we find, in the limit of exact θ 14 dominance where the other extra angles vanish, that ε NP K is too large. However, if one relaxes the exact θ 14 dominance limit, there exists a parameter region, where one may obtain ε NP K 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 L → π o νν.

Natural Suppression of FCNCs at the One-Loop Level in $Z^\prime$ Models with Implications for K, D and B Decays

“…This is evident from the expressions above and applies to all VLQ models. More recent calculations of this type in the context of vector-like models can be found in [33][34][35][36].…”