Model independent investigation of rare semileptonic b \to u l \bar{\nu}_l decay processes

Abstract

Motivated by the recent observation of lepton universality violation in the flavour changing charged current transitions $b \to c l \bar{\nu}_l$, we intend to scrutinize the lepton non-universality effects in rare semileptonic $B$ meson decays involving the quark level transitions $b \to u l \bar{\nu}_l$. In this regard, we envisage the model-independent approach and consider the generalized effective Lagrangian in the presence of new physics and constrain the new parameters by using the experimental branching fractions of $B_u^+ \to l^+ \nu_l$ and $B^- \to \pi^0 \mu^- \bar \nu_\mu$ processes, where $l=e, \mu, \tau$. We then estimate the branching ratios and forward-backward asymmetries of $B_{(s)} \to P (V)l \bar{\nu}_l$ processes, where $P(=K, \pi, \eta^{(\prime)})$ denotes the pseudoscalar meson and $V(=K^*, \rho)$ is the vector meson. We also find out various lepton non-universality parameters in these processes in the presence of new physics.