Exploring new physics in the C7-C7′ plane

Abstract

The Wilson coefficient C₇ 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 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 → X_sγ, 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 C₇, C₉, C₁₀ as well as their chirality-flipped counterparts. Within our framework, we find that we need to extend the constraints up to 1.6σ 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.