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

Abstract

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−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 |V ub | 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, B s,d → µ + µ − , B → {X s , K, K * }νν, and K → πνν decays. The possibility to explain a non-standard CP-violating phase in B s mixing in this context, and the comparison with other predictive new-physics frameworks addressing the same problem, is also discussed. While a large S ψφ asymmetry can easily be accommodated, we point out a tension in this framework between |V ub | and S ψK .

B→Xdγand constraints on new physics

“…This for example strongly disfavors the proposed best-fit solution to the right-handed CKM matrix of Ref. [29].…”

Additional information on heavy quark parameters from charged lepton forward-backward asymmetry

“…It will hopefully help to disentangle the tension with respect to the extraction of |V cb | utilising other methods or may contribute to solve some other puzzles in this decay mode [39]. It has been noted before [40,41], that right-handed currents may help to ease this tension, especially in b → u transitions. The relation between the transition to the heavy charm quark or light up quark is however model-dependent.…”

B → K ∗ ν ν ¯ $$ B\to {K}^{\left(\ast \right)}\nu \overline{\nu} $$ decays in the Standard Model and beyond

“…Most importantly, it has been pointed out that these correlations offer powerful tests of NP with new right-handed couplings and non-MFV interactions. Several of the formulae presented in that paper have been used since then in the study of a number of NP models [18][19][20][21][22][23][24][25]. For earlier studies of b → sνν transitions, see in particular [26,27].…”