CP violation and the 4th generation

TL;DR

This paper analyzes CP-violating processes involving 4th generation quarks within the Standard Model, providing predictions for asymmetries and decay modes that could be observed at Tevatron or LHC.

Contribution

It constructs a global fit for the 4th generation CKM matrix and predicts large CP asymmetries in specific decay channels, a novel analysis in this context.

Findings

High CP asymmetry in b'-> s(Z,H,gamma,g) decays, up to 90%.

Significant CP asymmetry (~15%) in t -> c g with 4th generation quarks.

Potential for discovery of 4th generation quarks at Tevatron or LHC.

Abstract

Within the Standard model with the 4th generation quarks b' and t' we have analyzed CP-violating flavor changing neutral current processes t -> cX; b'-> sX, b'-> bX,t'-> cX, and t'-> tX, with X=Z,H,gamma,g, by constructing and employing global, unique fit for the 4th generation mass mixing matrix CKM4 at 300 < m_t' < 700 GeV. All quantities appearing in the CKM4 were subject to our fitting procedure. We have found that our fit produces the following CP partial rate asymmetry dominance: a_CP(b'-> s(Z,H,gamma,g))= (90,73,52,30)%, at m_t' ~ 300,300,380,400 GeV, respectively. From the experimental point of view the best decay mode, out of the above four, is certainly b'-> s gamma, because of the presence of a clean high energy single final state photon. We have also obtained relatively large a_CP(t -> c g) ~ 15 (10)% for t' running in the loops with the mass m_t'= 650(500) GeV. There are fair chances that the 4th generation quarks will be discovered at Tevatron or LHC and that some of their decay rates shall be measured. If b' and t' exist at energies we assumed, with well executed tagging, large a_CP could be found too.