LAUSR

Abstract Motivated by the R D ( ⁎ ) anomalies in semileptonic B meson decay which can be explained by adding a single vector leptoquark U 3 ( 3 , 3 , 2 3 ) to the Standard Model, we further analyse the New Physics effects of vector leptoquark to the heavy baryon Ξ b → Ξ c τ − ν ¯ τ decay. Using the best-fit solutions for Wilson coefficients of operators resulted from experimental measurement R D ( ⁎ ) anomalies and the form factors resulted from relativistic quark model, we study the contributions of the leptoquark to several observables, such as differential branching ratio, ratio of differential branching ratio, lepton-side forward-backward asymmetry, longitudinal polarization fraction of Ξ c baryon and τ lepton as well as the convexity parameter of this decay with the helicity amplitude formalism. We find that the contributions of vector leptoquark to differential branching ratio, ratio of differential branching ratio and convexity parameter are significant which show deviations at high level from the corresponding Standard Model predictions. Nevertheless, the observables lepton-side forward-backward asymmetry, longitudinal polarization fraction of Ξ c baryon and τ lepton have the same behaviours in vector leptoquark as that in the Standard Model which displays the three observables are not sensitive to the New Physics effects of vector leptoquark.