Semileptonic b→c transitions, and in particular the ratios R(D(∗))=Γ(B→D(∗)τν)Γ(B→D(∗) ν), can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for R(D∗) is found to be more robust, because possible pollutions from B∗ contributions turn out to be negligibly small; this indicates that R(D∗) is a promising observable for searches of new physics.
Bibliographical noteFunding Information:
The work of C.S.K. was supported in part by the National Research Foundation grant funded by the government of Korea from the Ministry of Education, Science and Technology (Grant No.2016R1D1A1A02936965). A.V. acknowledges financial support from the Juan de la Cierva program (Grant No.27-13-463B-731) funded by the Spanish Ministerio de Economia y Competitividad as well as from the Spanish Grants No.FPA2014-58183-P, No.Multidark CSD2009-00064, No.SEV-2014-0398, and No.PROMETEOII/2014/084 (Generalitat Valenciana). G.L.C. and S.L.T. acknowledge financial support from Conacyt (Mexico) under Projects No.236394, No.263916, and No.296.
© 2017 American Physical Society.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)