Effects of Kaluza-Klein neutrinos on R_D and R_D^⁎

Recent measurements of RD and RD⁎ by the LHCb collaboration show deviations from their respective Standard Model values. These semileptonic B meson decays, associated with b→cτν¯ transition, are pointing toward new physics beyond the Standard Model via leptonic flavor universality violation. In this paper, we show that such anomaly can be resolved by the cummulative Kaluza-Klein (KK) modes of singlet right-handed neutrino which propagates in the large extra dimensional space. We found that the number of extra dimension should be 2 to explain RD and RD⁎. We show that both RD and RD⁎ constraint the energy scale MF of this extra dimension which are compatible with the limits from lepton flavor violating tau decays. In contrast, our findings are in tension with the limits coming from the neutrino experiments which set the most stringent lower bound on MF. The future measurements of RD(⁎)exp with reduced uncertainties will exclude this extra dimensional model with right-handed neutrino propagating in the bulk, if the central values stay.