Abstract
We point out that hints of deviations from unitarity in the first row of the CKM matrix may be explained by the presence of a single vector-like top. We study how the stringent experimental constraints arising from CP Violation in the kaon sector and from meson mixing such as {D}^0hbox{-} {overline{D}}^0,{K}^0hbox{-} {overline{K}}^0 and {B}_{d,s}^0hbox{-} {overline{B}}_{d,s}^0 can be satisfied in the proposed framework. In order for the deviations from unitarity to be of the required size while keeping the theory perturbative, the new top quark should have a mass mT ≲ 7 TeV which could be probed in upcoming experiments at the energy frontier.
Highlights
CKM matrix may be explained by the presence of a single vector-like top
It has been suggested [8] that the addition of a down-type (Q = −1/3) vectorlike isosinglet quark may lead to deviations from unitarity capable of accommodating the recent measurements of |Vus| and |Vud|
In this work we focus on the New Physics (NP) contributions to neutral meson mixing (D, K and Bd,s neutral-meson systems), and on the NP enhancement of the rare top decays t → qZ
Summary
Where Y u are the SM Yukawa couplings, φ denotes the Higgs doublet (φ = φ∗), Q0Li = u0Li d0Li T and u0Ri (i, j = 1, 2, 3) denote the SM quark doublets and up-type quark singlets, respectively. Y denotes Yukawa couplings to the extra right-handed field, while M and M correspond, at this level, to bare mass terms. The down-sector Yukawa Lagrangian is −Ld = Yidj Q0Li φ d0Rj + h.c. Note that the right-handed VLQ field TR0 is a priori indistinguishable from the SM fermion singlets u0Ri, since they possess the same quantum numbers. With Du = diag(mu, mc, mt, mT ), where mT is the mass of the new and heavy up-type quark T. The unitary rotations VL,R relate the flavour basis to the physical basis
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call