We study the phenomenological constraints and consequences in the flavor sector, of introducing a new fourth generation Z2 odd vector-like lepton doublet along with a Standard Model (SM) singlet scalar and an SU(2)L singlet scalar leptoquark carrying electromagnetic charge of +2/3, both odd under a Z2. We show that with little fine tuning among the various Yukawa couplings in the new physics (NP) Lagrangian along with the CKM parameters, the model is able to push the theoretical value of R(D∗)th from 0.252±0.003 to 0.263±0.051 and R(D)th from 0.300±0.008 to 0.313±0.158 compared to the SM value. Especially the NP contributions are able to reduce the discrepancy between experiment and theory of R(D∗) substantially compared to SM. This is quite impressive given that the model satisfy all other very stringent constrains coming from neutral meson oscillations and precision Z-pole data.
@article{arxiv.1806.01178,
title = {Implications of a vector-like lepton doublet and scalar Leptoquark on $R(D^{(*)})$},
author = {Lobsang Dhargyal and Santosh Kumar Rai},
journal= {arXiv preprint arXiv:1806.01178},
year = {2018}
}