New Physics Analysis of Some \(b\rightarrow u\ell \nu _\ell \) Transitions

The experimental measurements of the ratios \(R_{D^{(*)}}\) and \(R_{J/\psi }\) hint the presence of new physics beyond the standard model in \(b\rightarrow c\ell \nu _\ell \) transitions, as these values show a tension of about \((2-3)\sigma \) from their standard model predictions. Consequently, there has been an extensive search for new physics (NP) beyond the standard model in these transitions. One of the questions these observations pose is whether new physics effects can also manifest in \(b\rightarrow u\ell \nu _\ell \) transitions. In this regard, we study the decay modes \(B^{+}\rightarrow \eta ^{(\prime )}\ell ^+\nu _\ell \) mediated by \(b\rightarrow u\ell \nu _\ell \) transitions within an effective Lagrangian framework. We use the available experimental data on \(b \rightarrow u\) leptonic and semileptonic decays to constrain the parameter space of the relevant new physics couplings.