CPviolation in the semileptonicBl4 (B→Dπlν)decays: Multi-Higgs-doublet model and scalar-leptoquark models

$\mathrm{CP}$ violation from physics beyond the standard model is investigated in $B_{l4\mathrm{}}$ decays: $\overrightarrow{B}D\pi l{\overline{\nu }}_l.$ In the decay process, we include various excited states as intermediate states decaying to the final hadrons, $D+\pi$. We consider the semileptonic decay to a tau lepton family as well. $\mathrm{CP}$ violation is implemented through complex scalar-fermion couplings in the multi-Higgs-doublet model and scalar-leptoquark models beyond the standard model. With these complex couplings, we calculate the $\mathrm{CP}$-odd rate asymmetry and the optimal asymmetry. We find that for $B_{\tau 4}$ decays the optimal asymmetry is sizable and can be detected at $1\sigma$ level with about ${10}^6–{10}^{7}B$-meson pairs, for maximally allowed values of $\mathrm{CP}$-odd parameters in those extended models.