Exploring New Physics in the C7-C7' plane
Résumé
The Wilson coefficient C_7 governing the radiative electromagnetic decays of B meson has been calculated to a very high accuracy in the Standard Model, but till date there is no convincing model-independent experimental bound on either the magnitude or the sign of C_7. In the present paper, we attempt at constraining both the magnitude and sign of C_7 using a systematic approach. We consider already measured observables like the branching ratios of B --> Xs mu+ mu- and B --> Xs gamma, the isospin and CP asymmetries in B --> K* gamma, as well as A_FB and F_L in B --> K* l+ l-. We also discuss the transverse observable A_T^(2) which, once measured, may help to disentangle some of the scenarios considered. We explore the constraints on C_7, C_9, C_10 as well as their chirality-flipped counterparts. Within our framework, we find that we need to extend the constraints up to 1.6 sigma to allow for the "flipped-sign solution" of C_7. The SM solution for C_7 exhibits a very mild tension if New Physics is allowed in dipole operators only. We provide semi-numerical expressions for all these observables as functions of the relevant Wilson coefficients at the low scale.