Probing New Physics with $\bar{B}\to \ddot{I}(770){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ and $\bar{B}\to a_1(1260){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$

Abstract

The $B$ meson semileptonic modes to $\ddot{I}(770)$ and $a_1(1260)$ are useful to pin down possible non Standard Model effects. The 4d differential $\bar{B}\to \ddot{I}(\ddot{I}€\ddot{I}€){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ and $\bar{B}\to a_1(\ddot{I}\ddot{I}€){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ decay distributions are computed in SM and in extensions involving new Lepton Flavour Universality violating semileptonic $b\to u$ operators. The Large Energy limit for the light meson is also considered for both modes. The new effective couplings are constrained using the available data, and several observables in $\bar{B}\to \ddot{I}(\ddot{I}€\ddot{I}€){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ in which NP effects can be better identified are selected, using the angular coefficient functions. The complementary role of $\bar{B}\to \ddot{I}(\ddot{I}€\ddot{I}€){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ and $\bar{B}\to a_1(\ddot{I}\ddot{I}€){\ell }^{-}\bar{\hat{I}}{½}_{\ell }$ is discussed.

LaTeX, 39 pages, 21 figures. Discussion of the $a_1$ mode extended. References added