Quark flavour mixing with right-handed currents: An effective theory approach

The impact of right-handed currents in both charged- and neutral-current flavour-violating processes is analysed by means of an effective theory approach. More explicitly, we analyse the structure of dimension-six operators assuming a left–right symmetric flavour group, commuting with an underlying SU(2)L×SU(2)R×U(1)B−LSU(2)L×SU(2)R×U(1)B−L global symmetry, broken only by two Yukawa couplings. The model contains a new unitary matrix controlling flavour-mixing in the right-handed sector. We determine the structure of this matrix by charged-current data, where the tension between inclusive and exclusive determinations of |Vub||Vub| can be solved. Having determined the size and the flavour structure of right-handed currents, we investigate how they would manifest themselves in neutral current processes, including particle–antiparticle mixing, Z→bb¯, Bs,d→μ+μ−Bs,d→μ+μ−, B→{Xs,K,K⁎}νν¯, and K→πνν¯ decays. The possibility to explain a non-standard CP-violating phase in BsBs mixing in this context, and the comparison with other predictive new-physics frameworks addressing the same problem, is also discussed. While a large SψϕSψϕ asymmetry can easily be accommodated, we point out a tension in this framework between |Vub||Vub| and SψKSψK.