$B$ decay anomalies and dark matter from vectorlike confinement

Abstract

Lepton flavor universality violating $B\to K\ell\ell$ and $K^*\ell\ell$ decays tentatively observed by LHCb can be explained by leptoquark exchange. We explore a simple model for the $B$ anomalies with a composite leptoquark from new strong dynamics at the TeV scale, a confining SU($N_{\rm HC}$) hypercolor interaction. The new matter fields, fundamentals under SU($N_{\rm HC}$), are heavy vectorlike fermions $\Psi,\, S,$ and an inert scalar doublet $\phi$. $\Psi$ is colored under QCD while $S$ is neutral, and the hyperbaryon $S^N$ is a dark matter candidate. The model is tightly constrained by meson-antimeson oscillations, lepton flavor violation, and LHC searches for resonant production of the exotic bound states. The dark matter may be detectable through its magnetic dipole moment. If $m_S$ is sufficiently small, composite leptoquarks and heavy lepton partners can be pair-produced at an observable level at LHC.