Jérôme Charles

Anatomy of new physics in B-B mixing

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.

Predictions of selected flavour observables within the Standard Model

This letter gathers a selection of Standard Model predictions issued from the metrology of the CKM parameters performed by the CKMfitter group. The selection includes purely leptonic decays of neutral and charged B, D and K mesons. In the light of the expected measurements from the LHCb experiment, a special attention is given to the radiative decay modes of B mesons as well as to the B-meson mixing observables, in particular the semileptonic charge asymmetries a^d,s_SL which have been recently investigated by the D0 experiment at Tevatron. Constraints arising from rare kaon decays are addressed, in light of both current results and expected performances of future rare kaon experiments. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

Current status of the Standard Model CKM fit and constraints on

This letter summarises the status of the global fit of the CKM parameters within the Standard Model performed by the CKMfitter group. Special attention is paid to the inputs for the CKM angles

\Delta F=2

\alpha

New Physics

and

Constraints on new physics in

\gamma

B-\bar{B}

and the status of

mixing in the light of recent LHCb data

B_s\to\mu\mu

Future sensitivity to new physics in B_d, B_s and K mixings

and

Modeling theoretical uncertainties in phenomenological analyses for particle physics

B_d\to \mu\mu