Sébastien Descotes-Genon

Understanding the

We present a global analysis of the B->K*(->K pi)mu+mu- decay using the recent LHCb measurements of the primary observables P_{1,2} and P_{4,5,6,8}. Some of them exhibit large deviations with respect to the SM predictions. We explain the observed pattern of deviations through a large New Physics contribution to the Wilson coefficient of the semileptonic operator O9. This contribution has an opposite sign to the SM one, i.e., reduces the size of this coefficient significantly. A good description of data is achieved by allowing for New Physics contributions to the Wilson coefficients C7 and C9 only. We find a 4.5 sigma deviation with respect to the SM prediction, combining the large-recoil B->K*(->K pi)mu+mu- observables with other radiative processes. Once low-recoil observables are included the significance gets reduced to 3.7 sigma. We have tested different sources of systematics, none of them modifying our conclusions significantly. Finally, we propose additional ways of measuring the primary observables through new foldings.

B\to K^*\mu^+\mu^-

A bstractWe present a detailed discussion of the current theoretical and experimental situation of the anomaly in the angular distribution of B → K*(→ Kπ)μ+μ−, observed at LHCb in the 1 fb−1 dataset and recently confirmed by the 3 fb−1 dataset. The impact of this data and other recent measurements on b → sℓ+ℓ− transitions (ℓ = e, μ) is considered. We review the observables of interest, focusing on their theoretical uncertainties and their sensitivity to New Physics, based on an analysis employing the QCD factorisation approach including several sources of hadronic uncertainties (form factors, power corrections, charm-loop effects). We perform fits to New Physics contributions including experimental and theoretical correlations. The solution that we proposed in 2013 to solve the B → K*μ+μ− anomaly, with a contribution C9NP≃−1

Global analysis of b → sℓℓ anomalies

{mathcal{C}}_9^{mathrm{NP}}simeq -1

Optimizing the basis of B → K*ℓ+ℓ− observables in the full kinematic range

, is confirmed and reinforced. A wider range of New-Physics scenarios with high significances (between 4 and 5 σ) emerges from the fit, some of them being particularly relevant for model building. More data is needed to discriminate among them conclusively. The inclusion of b → se+e− observables increases the significance of the favoured scenarios under the hypothesis of New Physics breaking lepton flavour universality. Several tests illustrate the robustness of our conclusions.

Implications from clean observables for the binned analysis of B → K ∗ μ + μ − at large recoil

We analyse three different New Physics scenarios for Delta F=2 flavour-changing neutral currents in the quark sector in the light of recent data on neutral-meson mixing. We parametrise generic New Physics contributions to Bq - Bq-bar mixing (q=d,s), in terms of one complex quantity Delta_q, while three parameters Delta_K^{tt}, Delta_K^{ct} and Delta_K^{cc} are needed to describe K - Kbar mixing. In Scenario I, we consider uncorrelated New Physics contributions in the Bd, Bs, and K sectors. In this scenario, it is only possible to constrain the parameters Delta_d and Delta_s whereas there are no non-trivial constraints on the kaon parameters. In Scenario II, we study the case of Minimal Flavour Violation (MFV) and small bottom Yukawa coupling, where Delta=Delta_d=Delta_s=Delta_K^{tt}. We show that Delta must then be real, so that no new CP phases can be accomodated, and express the remaining parameters Delta_K^{cc} and Delta_K^{ct} in terms of Delta in this scenario. Scenario III is the generic MFV case with large bottom Yukawa couplings. In this case, the Kaon sector is uncorrelated to the B_d and B_s sectors. As in the second scenario one has Delta_d=Delta_s=Delta, however, now with a complex parameter Delta. Our quantitative analyses consist of global CKM fits within the Rfit frequentist statistical approach, determining the Standard Model parameters and the new physics parameters of the studied scenarios simultaneously. We find that the recent measurements indicating discrepancies with the Standard Model are well accomodated in Scenarios I and III with new mixing phases, with a slight preference for Scenario Ithat permits different new CP phases in the Bd and Bs systems. Within our statistical framework, we find that the Standard-Model hypothesis Delta_d=Delta_s=1 is disfavoured with p-values of 3.4 sigma and 3.1 sigma in Scenarios I and III respectively.

The determination of α S from τ decays revisited

A bstractWe discuss the observables for the B → K*(→ Kπ)ℓ+ℓ− decay, focusing on both CP-averaged and CP-violating observables at large and low hadronic recoil with special emphasis on their low sensitivity to form-factor uncertainties. We identify an optimal basis of observables that balances theoretical and experimental advantages, which will guide the New Physics searches in the short term. We discuss some advantages of the observables in the basis, and in particular their improved sensitivity to New Physics compared to other observables. We present predictions within the Standard Model for the observables of interest, integrated over the appropriate bins including lepton mass corrections. Finally, we present bounds on the S-wave contribution to the distribution coming from the

On the impact of power corrections in the prediction of B → K*μ+μ− observables

Bto K_0^{*}{ell^{+}}{ell^{-}}

Predictions of selected flavour observables within the Standard Model

decay, which will help to establish the systematic error associated to this pollution.