SAIP2025

Probing Charged Current B-anomalies via a U (1)μ−τ Extension of the Standard Model

11 Jul 2025, 10:50

20m

Solomon Mahlangu House (University of the Witwatersrand, Johannesburg)

Oral Presentation Track B - Nuclear, Particle and Radiation Physics Nuclear, Particle and Radiation Physics-2

Speaker

Mr Vuyolwethu Happyboy Kakancu (University of Witwatersrand)

Description

The lepton flavor universality ratios $R(D)$ and $R(D^{*})$, defined as $R_{D^{(*)}} \equiv \mathcal{B}(\bar{B}\to D^{(*)} \tau^{-} \bar{\nu}_{\tau})/\mathcal{B}(\bar{B} \to D^{(*)} \ell^{-} \bar{\nu}_{\ell})$ where$(\ell = e, \mu)$, are measured in semi-leptonic $B$ decays and serve as sensitive probes of new physics beyond the Standard Model (SM). Recent experimental averages, $R(D) = 0.342 \pm 0.026$ and $R(D^*) = 0.287 \pm 0.012$, show a combined deviation of $3.2\sigma$ from SM predictions, indicating the possibility of new physics in semi-leptonic $B$ meson decays. We base our attention on the Charge Current$(CC)$ process $b\to c\tau^{-}\bar{\nu_{\tau}}$, where we explore this process using a well-motivated extension of the SM, featuring a $U(1)_{\mu - \tau}$ gauge symmetry. The model introduces new vector-like quark doublets $( Q'_a )$ and a singlet scalar $( \chi )$, both charged under $U(1)_{\mu - \tau}$ and odd under $Z_2$ symmetry. The corresponding Wilson coefficients are derived and a $\chi^2$-fit is performed with the current experimental data to constrain the model parameters.