Exploring new physics in the C 7-C 7′ plane

The Wilson coefficient C 7 governing the radiative electromagnetic decays of B meson has been calculated toa very high accuracy in the Standard Model, but experimental bounds on either the magnitude or the sign of C 7 are often model-dependent. 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 → X s μ + μ − and B → X s γ, the isospin and CP asymmetries in B → K ∗ γ, 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 1.6σ 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.