Understand
We construct a scalar dark matter model with $U(1)_{L_\mu-L_\tau}$ symmetry in which the dark matter interacts with the quark flavours, allowing lepton non-universal $b \to s \ell \bar{\ell}$ decays.
- The model can solve $b \to s \mu \mu$ ($R_{K^{(*)}}$) anomaly and accommodate the relic abundance of dark matter simultaneously while satisfying the constraints from other low energy flavour experiments and direct detection experiments of dark matter.
- The new fields include vector-like heavy quarks $U$ and $D$, $U(1)_{L_\mu-L_\tau}$ breaking scalar $S$, as well as the dark matter candidate $X_I$ and its heavy partner $X_R$.
- To explain both $b \to s \mu \mu$ anomaly and the dark matter, {\it i)} large mass difference between $X_R$ and $X_I$ is required, {\it ii)} electroweak scale dark matter and heavy quarks are favoured, {\it iii)} not only electroweak scale but ${\cal O}(10)$ TeV dark gauge boson $Z'$ and $X_R$ are allowed.