A new model-independent way of extracting |Vub/Vcb| Original Research Article

The ratio between the photon spectrum in B→Xsγ and the differential semileptonic rate with respect to the hadronic variable MX/EX is a short-distance quantity calculable in perturbation theory and independent of the Fermi motion of the b quark in the B meson. We present a NLO analysis of this ratio and show how it can be used to determine |Vub/Vcb| independently of any model for the shape function. We also discuss how this relation can be used to test the validity of the shape-function theory on the data.