Anatomy of new physics in B-B mixing

We analyze three different new physics scenarios for ΔF=2 flavor-changing neutral currents in the quark sector in the light of recent data on neutral-meson mixing. We parametrize generic new physics contributions to Bq-Bq mixing, q=d, s, in terms of one complex quantity Δq, while three parameters ΔKtt, ΔKct, and ΔKcc are needed to describe K-K 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 Δd and Δs whereas there are no nontrivial constraints on the kaon parameters. In scenario II, we study the case of minimal flavor violation (MFV) and small bottom Yukawa coupling, where Δ≡Δd=Δs=ΔKtt. We show that Δ must then be real, so that no new CP phases can be accommodated, and express the remaining parameters ΔKcc and ΔKct in terms of Δ 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 Bd and Bs sectors. As in the second scenario one has Δd=Δs≡Δ, however, now with a complex parameter Δ. Our quantitative analyses consist of global Cabibbo-Kobayashi-Maskawa (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 accommodated in Scenarios I and III with new mixing phases, with a slight preference for Scenario I that permits different new CP phases in the Bd and Bs systems. Within our statistical framework, we find evidence of new physics in both Bd and Bs systems. The standard model hypothesis Δd=Δs=1 is disfavored with p-values of 3.6σ and 3.3σ in Scenarios I and III, respectively. We also present an exhaustive list of numerical predictions in each scenario. In particular, we predict the CP phase in Bs→J/ψφ and the difference between the Bs and Bd semileptonic asymmetries, which will be both measured by the LHCb experiment.