Exploring new physics in the C7-C7' plane

Abstract

The Wilson coefficient C7 governing the radiative electromagnetic decays of B meson has been calculated to a very high accuracy in the Standard Model, but experimental bounds on either the magnitude or the sign of C7 are often model-dependent. In the present paper, we attempt at constraining both the magnitude and sign of C7 using a systematic approach. We consider already measured observables like the branching ratios of B → X sμ+μ- and B → Xs γ , the isospin and CP asymmetries in B → K*γ , as well as AFB and FL in B → K*l+l-. We also discuss the transverse observable A(2)T which, once measured, may help to disentangle some of the scenarios considered. We explore the constraints on C7,C9,C10 as well as their chirality-flipped counterparts. Within our framework, we find that we need to extend the constraints up to 1.6 δ to allow for the "flipped-sign solution" of C7. The SM solution for C7 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.