We analyse the present experimental evidence for a complex CKM matrix, even
allowing for New Physics contributions to ϵK, aJ/ΨKS%,
ΔMBd, ΔMBs, and the ΔI=1/2 piece of ρρ and B→ρπ. We emphasize the crucial r\^{o}le played by
the angle γ in both providing irrefutable evidence for a 3×3
complex CKM matrix and placing constraints on the size of NP contributions. It
is shown that even if one allows for New Physics a real CKM matrix is excluded
at a 99.92% C.L., and the probability for the phase γ to be in the
interval [−170∘;−10∘]∪[10∘;170∘] is
99.7%. Large value of the phase χ, e.g. of order λ, is only
possible in models where the unitarity of the 3×3
Cabibbo-Kobayashi-Maskawa matrix is violated through the introduction of extra
Q=2/3 quarks. We study the allowed range for χ and the effect of a
large χ on various low-energy observables, such as CP asymmetries in B
meson decays. We also discuss the correlated effects which would be observable
at high energy colliders, like decays t→cZ, etc..Comment: 14 pages, 7 figures. Presented at the Symposium in Honour of Gustavo
C. Branco "CP Violation and the Flavour Puzzle", Lisbon, Portugal, 19-20 July
2005. To appear in Acta Physica Polonica