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

Abstract

In 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.

Phenomenology analysis of $$\bar{B}^* \rightarrow V \tau ^-\bar{\nu }_{\tau }$$ decays in and beyond the Standard Model

“…2.3 within the SM and in above various NP benchmark points in a model independent way. From our precious works [54,55], it is noteworthy that the variation of different observables for the decay processes B * → V τ − ντ (V = D * u,d , D * s , J/ ) are similar to each other. In order to avoid repetition, we will take B * − → D * 0 τ − ντ as an example to illustrate in detail and display the q 2 dependency of each observable for this decay, as well as the same goes in following text.…”

“…Furthermore, many works have been done based on the model independent framework [30][31][32][33][34][35] and some specific NP models by introducing new particles, such as charged Higgses model [36][37][38][39], R-parity violating supersymmetric models [40][41][42][43][44] and leptoquarks model [45][46][47][48][49]. And the NP effects can affect the corresponding b → c(u) ν processes, such as bottom meson decay processes B c → J/ψ(η c ) ν [17][18][19][20]50,51], B ( * ) → P(V ) ν [32,[52][53][54][55] and bottom baryons decay processes…”

“…where the superscripts i, j represent the combination of the operators V ± A and S ± P. One can refer to Refs. [32,54,55] for more details.…”