A theory of R(D*, D) anomaly with right-handed currents
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© 2019, The Author(s). We present an ultraviolet complete theory for the R(D*) and R(D) anomaly in terms of a low mass WR± gauge boson of a class of left-right symmetric models. These models, which are based on the gauge symmetry SU(3)c × SU(2)L × SU(2)R × U(1)B − L, utilize vector-like fermions to generate quark and lepton masses via a universal seesaw mechanism. A parity symmetric version as well as an asymmetric version are studied. A light sterile neutrino emerges naturally in this setup, which allows for new decay modes of B-meson via right-handed currents. We show that these models can explain R(D*) and R(D) anomaly while being consistent with LHC and LEP data as well as low energy flavor constraints arising from KL−KS,Bd,s−B¯d,s,D−D¯ mixing, etc., but only for a limited range of the WR mass: 1.2 (1.8) TeV ≤ MWR ≤ 3 TeV for parity asymmetric (symmetric) Yukawa sectors. The ratio R(D)/R(D*) is predicted to be ≃ 1.16, which is the same as in the Standard Model. The light sterile neutrinos predicted by the model may be relevant for explaining the MiniBoone and LSND neutrino oscillation results. The parity symmetric version of the model provides a simple solution to the strong CP problem without relying on the axion. It also predicts an isospin singlet top partner with a mass MT = (1.5 − 2.5) TeV.
author list (cited authors)
Babu, K. S., Dutta, B., & Mohapatra, R. N.