Can the Differences in the Determinations ofVubandVcbBe Explained by New Physics?

Abstract

The precise determination of the Cabibbo-Kobayashi-Maskawa elements V(ub) and V(ub) is crucial for any new physics analysis in the flavor sector. Their values can be determined from several tree-level decays: V(ub) can be extracted from B→Dℓν and B→D(*)ℓν while V(ub) can be obtained from B→πℓν, B→ρℓν, and B→τν. In addition, for both V(ub) and V(ub) an inclusive determination is available. There is a long lasting discrepancy between the inclusive and exclusive determinations which recently even increased for V(ub) above the 3σ level. In this Letter we study the possible effect of new physics on the inclusive and exclusive determination of V(ub) and V(ub) in a model independent way. We find that there is only one operator corresponding to a modified W coupling which can achieve this. However, respecting SU(2) gauge invariance at the high scale this would lead to very large violations of the Z to bb̅ coupling not compatible with experiment. Therefore, we conclude that a new physics explanation of the difference between the inclusive and exclusive determination of V(ub) and V(ub) is currently ruled out. Therefore, the discrepancies must be due to underestimated uncertainties in the theoretical and/or the experimental analysis.