Isospin in B decays and the (B0B̄0)/(B+B-) production ratio

Methods are proposed for measuring the ratio R+/0=Γ(Υ(4S) →B+B-)/Γ(Υ(4S)→B0B̄0) without assuming isospin invariance in exclusive hadronic decays such as B→J/ψK. The validity of isospin invariance in various B decays is discussed. Isospin violations are expected to be especially small in inclusive semileptonic decays, so that Γ(B+→Xc0+ν)=Γ(B0→Xc-+ν) is expected to hold at the subpercent level. Suggestions are made for utilizing this relation. The accuracy of a "double-tag" method for obtaining R+/0, such as that used for measuring the D+D-/D0D̄0 ratio at the ψ′′≡ψ(3770) , is also estimated.