Investigation on the New Physics effects of the vector leptoquark on semileptonic $$\bar{B}^*\rightarrow V \tau ^-\bar{\nu _{\tau }}$$ decays

Abstract

AbstractIn recent years, the experimental results about the ratio of the branching ratios $$R_{D^{(*)}}$$ R D ( ∗ ) and $$R_{K^{(*)}}$$ R K ( ∗ ) , which are in the semileptonic $$b\rightarrow c l \bar{\nu }_{l}$$ b → c l ν ¯ l and $$b\rightarrow s l^+l^-$$ b → s l + l - decays, have been observed to deviate from the Standard Model prediction by $$1.4\sigma $$ 1.4 σ , $$2.5\sigma $$ 2.5 σ , $$2.4\sigma $$ 2.4 σ and $$2.2\sigma $$ 2.2 σ respectively. Motivated by these anomalies and by the abundant $$B^*$$ B ∗ data samples, we investigate possible New Physics effects of the vector leptoquark in the semileptonic decay $$\bar{B}^*_{u,d,s,c} \rightarrow V \tau ^-\bar{\nu }_{\tau }$$ B ¯ u , d , s , c ∗ → V τ - ν ¯ τ ($$V=D^*_{u,d,s},J/\psi $$ V = D u , d , s ∗ , J / ψ ). which is induced by $$b\rightarrow c \tau ^-\bar{\nu }_{\tau }$$ b → c τ - ν ¯ τ 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 $$d{\varGamma }^{(L)}/dq^2(\bar{B}^*_{u,d,s,c} \rightarrow V \tau ^-\bar{\nu }_{\tau })$$ d Γ ( L ) / d q 2 ( B ¯ u , d , s , c ∗ → V τ - ν ¯ τ ) and $$R^{*(L)}_{V}(q^2)$$ R V ∗ ( 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 $$A_{FB}^{\tau }(q^2)$$ A FB τ ( q 2 ) , $$P_{\tau }(q^2)$$ P τ ( q 2 ) and $$F_{L}^{*V}(q^2)$$ F L ∗ V ( q 2 ) . We hope that the numerical results in this work will be tested in the future high energy experiments.