Flavor changing neutral current processes in B decays

Abstract

Flavor changing neutral current (FCNC) processes in B decays are discussed in the context of the standard model (SM). Making use of the QCD‐improved effective Hamiltonian describing the so‐called ‖ΔB‖=1, ΔQ=0, and ‖ΔB‖=2, ‖ΔQ‖=0 transitions, rates and differential distributions in a number of B decays are presented. The FCNC processes discussed here include the radiative decays B→Xs+γ, B→Xd+γ, and the semileptonic decays B→Xsl+l−, B→Xdl+l−, B→Xsνlν̄l, and B→Vdνlν̄l. Some selected exclusive processes such as (Bu,Bd)→K*+γ, Bd→ω+γ, (Bu,Bd)→ρ+γ, Bs→(φ,K*)+γ, and (Bd,Bs)→l+l− are also reviewed. Implications of the measurements of the B0d − B0d mixing ratio xd≡ΔM/Γ=0.69±0.09, the electromagnetic penguin dominated decay rate, BR(B→K*+γ)=4.5±1.0±0.9)×10−5 and the experimental upper limit BR(B→X+γ)<5.4×10−4 for the SM parameters are also discussed. The SM‐based predictions are quantified for FCNC B decays and the prospects of determining the CKM matrix elements from their eventual measurements are discussed.