[en] In recent years, the experimental results about the ratio of the branching ratios R${}_{D^{(\ast <!--\; ???\; -->)}}$ and R${}_{K^{(\ast <!--\; ???\; -->)}}$, which are in the semileptonic b → cl → ${\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_l$ and b → sl${}^{+}$l${}^{-<!--\; ???\; -->}$ decays, have been observed to deviate from the Standard Model prediction by 1.4σ, 2.5σ, 2.4σ and 2.2σ respectively. Motivated by these anomalies and by the abundant B${}^{\ast <!--\; ???\; -->}$ data samples, we investigate possible New Physics effects of the vector leptoquark in the semileptonic decay ${\stackrel{¯<!--\; ??\; -->}{B}}_{u,d,s,c}^{\ast <!--\; ???\; -->}$ → Vτ${}^{-<!--\; ???\; -->}$${\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$ (V=D${}_{u,d,s}^{\ast <!--\; ???\; -->}$, J//psi). which is induced by b → cτ${}^{-<!--\; ???\; -->}$${\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$ at the quark level. Using the best fit solutions for the new operator Wilson coefficients and the relevant form factors which are obtained in the light-front quark model, we find that (i) the contributions of the vector leptoquark to dΓ${}^{(L)}$/dq${}^2$(${\stackrel{¯<!--\; ??\; -->}{B}}_{u,d,s,c}^{\ast <!--\; ???\; -->}$ → Vτ${}^{-<!--\; ???\; -->}$${\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$ and $R_V^{\ast <!--\; ???\; -->(L)}(q^2)$ to be significant; (ii) the two best fit solutions in the vector leptoquark are indistinguishable from each other and give similar amounts of enhancements to these two observables; (iii) both two cases of the vector leptoquark give nearly same results as those of the Standard Model for A${}_{FB}^{\mathrm{\tau <!--\; ??\; -->}}$(q${}^2$) , P${}_{\mathrm{\tau <!--\; ??\; -->}}$(q${}^2$) and F${}_L^{\ast <!--\; ???\; -->V}$(q${}^2$). We hope that the numerical results in this work will be tested in the future high energy experiments.

[en] Recently, the Belle collaboration reported the first measurement of the τ lepton polarization P _τ(D*) in $\stackrel{¯<!--\; ??\; -->}{B}\to <!--\; ???\; -->D^{\ast <!--\; ???\; -->}{\mathrm{\tau <!--\; ??\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$ decay and a new measurement of the rate of the branching ratios R(D*), which are consistent with the Standard Model (SM) predictions. These could be used to constrain the New Physics (NP) beyond the SM. In this paper, we probe $\stackrel{¯<!--\; ??\; -->}{B}\to <!--\; ???\; -->D^{(\ast <!--\; ???\; -->)}{\mathrm{\ell <!--\; ???\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\ell <!--\; ???\; -->}}$ (ℓ = e, μ, τ) decays in the model-independent way and in the specific G(221) models with lepton flavour universality. Considering the theoretical uncertainties and the experimental errors at the 95% C.L., we obtain the quite strong bounds on the model-independent parameters $C_{\mathrm{L}\mathrm{L}}^{\mathrm{\prime <!--\; ???\; -->}},C_{\mathrm{L}\mathrm{R}}^{\mathrm{\prime <!--\; ???\; -->}},C_{\mathrm{R}\mathrm{R}}^{\mathrm{\prime <!--\; ???\; -->}},C_{\mathrm{R}\mathrm{L}}^{\mathrm{\prime <!--\; ???\; -->}},g_V,g_A,g_V^{\mathrm{\prime <!--\; ???\; -->}},g_A^{\mathrm{\prime <!--\; ???\; -->}}$ and the specific G(221) model parameter rates. We find that the constrained NP couplings have no obvious effects on all (differential) branching ratios and their rates, nevertheless, many NP couplings have very large effects on the lepton spin asymmetries of $\stackrel{¯<!--\; ??\; -->}{B}\to <!--\; ???\; -->D^{(\ast <!--\; ???\; -->)}{\mathrm{\ell <!--\; ???\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\ell <!--\; ???\; -->}}$ decays and the forward–backward asymmetries of $\stackrel{¯<!--\; ??\; -->}{B}\to <!--\; ???\; -->D^{\ast <!--\; ???\; -->}{\mathrm{\ell <!--\; ???\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\ell <!--\; ???\; -->}}$. So we expect precision measurements of these observables would be researched by LHCb and Belle-II. (paper)

[en] Motivated by the persistent anomalies reported in the b $\to <!--\; ???\; -->$ c$\mathrm{\tau <!--\; ??\; -->}\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}$ data, we investigate the semileptonic decays ${\stackrel{¯<!--\; ??\; -->}{B}}^{\ast <!--\; ???\; -->}$$\to <!--\; ???\; -->$ V${\mathrm{\tau <!--\; ??\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$ (V=D${}_{u,d,s}^{\ast <!--\; ???\; -->}$, J/$\mathrm{\psi <!--\; ??\; -->}$), within the Standard Model and beyond. The relevant transition form factors, being calculated in the covariant light-front quark model, is the main source of theoretical uncertainties. Using various best-fit solutions for the new operator Wilson coefficients, we report numerical results on various observables related to the processes ${\stackrel{¯<!--\; ??\; -->}{B}}^{\ast <!--\; ???\; -->}$$\to <!--\; ???\; -->$ V${\mathrm{\tau <!--\; ??\; -->}}^{-<!--\; ???\; -->}{\stackrel{¯<!--\; ??\; -->}{\mathrm{\nu <!--\; ??\; -->}}}_{\mathrm{\tau <!--\; ??\; -->}}$, such as the branching ratios, the ratio of branching fractions, the hadron and lepton polarization asymmetries, the forward-backward asymmetries and the convexity parameter. We also predict the q${}^2$ distribution of these observables both within the Standard Model and in various new physics scenarios. The accessible observables are studied in order to assess their sensitivity to the different new physics scenarios. We can find that some of the new physics scenarios can be differentiated from each other by using these observables and their correlations. We also find that some observables of these decay modes are sizeable and deviate significantly (for new physics coupling parameter S${}_R$ especially) from their corresponding standard model values, which are expected to be within the reach of Run III of Large Hadron Collider experiment. And experimental information on these distributions which will be testified in the future can help to disentangle the dynamical origin of the current anomalies.

[en] Motivated by recent $R_D$, $R_{D^{⁎}}$ and $R_{J/\psi }$ anomalies in $B\to D{\ell }^{-}{\overline{\nu }}_{\ell }$, $B\to D^{⁎}{\ell }^{-}{\overline{\nu }}_{\ell }$ and $B_c\to J/\psi {\ell }^{-}{\overline{\nu }}_{\ell }$ decays, respectively, we study possible R-parity violating supersymmetric effects in $B_c\to J/\psi {\ell }^{-}{\overline{\nu }}_{\ell },{\eta }_c{\ell }^{-}{\overline{\nu }}_{\ell }$ and ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c{\ell }^{-}{\overline{\nu }}_{\ell }$ decays, which are also induced by $b\to c{\ell }^{-}{\overline{\nu }}_{\ell }$ at quark level. We find that (I) the constrained slepton exchange couplings ${\lambda }_{i33}{\tilde{\lambda }}_{i23}^{\prime ⁎}$ involving in $b\to c{\tau }^{-}{\overline{\nu }}_{\tau }$ transition from relevant latest experimental data still have quite large effects on all (differential) branching ratios and the normalized forward–backward asymmetries of the exclusive semileptonic $b\to c{\tau }^{-}{\overline{\nu }}_{\tau }$ decays as well as the ratios of the (differential) branching ratios; (II) after satisfying the data of $R_D$ and $R_{D^{⁎}}$, the upper limit of $R_{J/\psi }$, $R_{{\eta }_c}$ and $R_{{\mathrm{\Lambda }}_c}$ could be increased by 10%, 112% and 24%, respectively, from their upper limits of the Standard Model predictions by the ${\lambda }_{i33}{{\tilde{\lambda }}^{\prime ⁎}}_{i23}$ couplings. The results in this work could be used to probe R-parity violating effects and will correlate with searches for direct supersymmetric signals at the running LHCb and the forthcoming Belle-II.

[en] Inspired by the recent anomaly measurements of the lepton-flavor violating decays $h\to \mu \tau$ and the lepton flavor non-universality in decays $\overline{b}\to \overline{s}{\ell }^{-}{\ell }^{+}$, we investigate the lepton flavor violating exclusive $\overline{b}\to \overline{s}{\ell }_i^{-}{\ell }_j^{+}$($i\ne j$ and $\ell =e,\mu ,\tau$) decays within supersymmetry. Relevant R-parity violating couplings are constrained by using the latest experimental upper limits on the branching ratios of $B_s\to {\ell }_i^{-}{\ell }_j^{+}$ and $B\to K^{(⁎)}{\ell }_i^{-}{\ell }_j^{+}$ flavor changing neutral current processes, and we find that all relevant branching ratios are very sensitive to the moduli of the squark and sneutrino exchange coupling products. In addition, the constrained lepton number violating effects on the dilepton invariant mass spectra, the single lepton polarization asymmetries and the differential forward–backward asymmetries are also studied. These lepton-flavor violating B decays could be used for the search of lepton flavor violation at the running LHC and the forthcoming Belle-II.