Lawrence Berkeley National Laboratory

We propose novel methods to determine the υ (4S)→B+B- and υ (4S)→B0B¯0 decay rates. The precision to which they and their ratio are known yields at present a limiting uncertainty around 2% in measurements of absolute B decay rates, and thus in a variety of applications, such as precision determinations of elements of the Cabibbo-Kobayashi-Maskawa matrix and flavor-symmetry relations. The new methods we propose are based in one case on exploiting the υ (5S) datasets, in the other case on the different average number of charged tracks in B± and B0 decays. We estimate future sensitivities using these methods and discuss possible measurements of fd/fu at the (HL-)LHC.