Z′models with less-minimal flavour violation

TLDR: In this article, the authors study the phenomenology of simplified Z′ models with a global U(2)3 flavour symmetry in the quark sector, broken solely by the Standard Model Yukawa couplings.

Abstract: We study the phenomenology of simplified Z′ models with a global U(2)3 flavour symmetry in the quark sector, broken solely by the Standard Model Yukawa couplings. This flavour symmetry, known as less-minimal flavour violation, protects ΔF=2 processes from dangerously large new physics (NP) effects, and at the same time provides a free complex phase in b→s transitions, allowing for an explanation of the hints for additional direct CP violation in kaon decays (ϵ′/ϵ) and in hadronic B-decays (B→Kπ puzzle). Furthermore, once the couplings of the Z′ boson to the leptons are included, it is possible to address the intriguing hints for NP (above the 5σ level) in b→sl+l− transitions. Taking into account all flavour observables in a global fit, we find that ϵ′/ϵ, the B→Kπ puzzle and b→sl+l− data can be explained simultaneously. Sizeable CP violation in b→sl+l− observables, in particular A8, is predicted, which can be tested in the near future, and an explanation of the B→Kπ and ϵ′/ϵ puzzles leads to effects in di-jet tails at the LHC, that are not far below the current limits. Once b→sl+l− is included, cancellations in di-muon tails, possibly by a second Z′, are required by LHC data.