Abstract
The B → K ∗ μμ decay exhibits deviations with respect to Standard Model expectations and the measurement of the ratio R K hints at a violation of lepton-flavour universality in B → Kll transitions. Both effects can be understood in model-independent fits as a short-distance contribution to the Wilson coefficient C 9μ , with some room for similar contributions in other Wilson coefficients for b → sμμ transitions. We discuss how a full angular analysis of B → K ∗ ee and its comparison with B → K ∗ μμ could improve our understanding of these anomalies and help confirming their interpretation in terms of short-distance New Physics. We discuss several observables of interest in this context and provide predictions for them within the Standard Model as well as within several New Physics benchmark scenarios. We pay special attention to the sensitivity of these observables to hadronic uncertainties from SM contributions with charm loops.
Highlights
Operator in the effective Hamiltonian [17] for b → sμμ, as initially discussed in ref. [1] and later confirmed by several works [18,19,20,21,22,23,24]
We discuss how a full angular analysis of B → K∗ee and its comparison with B → K∗μμ could improve our understanding of these anomalies and help confirming their interpretation in terms of short-distance New Physics
It is interesting to investigate these issues by considering specific observables with different sensitivity to transversity-dependent and independent long-distance charm contributions, as well as to lepton flavour non-universality (LFNU) New Physics
Summary
In the presence of NP, all observables Qi, Ti and Bi are in principle affected by long-distance charm loop contributions in C9, both transversity-independent and transversity-dependent. It is interesting to investigate these issues by considering specific observables with different sensitivity to transversity-dependent and independent long-distance charm contributions, as well as to LFNU New Physics. One can think of exploiting the angular coefficients in electron and muon modes in order to build observables only sensitive to some of the Wilson coefficients, and in some cases, insensitive to transversity-independent long-distance charm contributions. If there is no NP in δC10 M becomes insensitive to transversity-independent charm effects at leading order and at large recoil. The behaviour of B5 (B5), B6s (B6s) and M (M ) in specific q2regions should provide powerful tests of physics beyond the SM, with a limited sensitivity to hadronic uncertainties
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