Hidden sector explanation of $B$-decay and cosmic ray anomalies

There are presently several discrepancies in $b\to s{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decays of $B$ mesons suggesting new physics coupling to $b$ quarks and leptons. We show that a $Z^{\mathrm{\prime }}$, with couplings to quarks and muons that can explain the $B$-decay anomalies, can also couple to dark matter in a way that is consistent with its relic abundance, direct detection limits, and hints of indirect detection. The latter include possible excess events in antiproton spectra recently observed by the AMS-02 experiment. We present two models, having a heavy (light) $Z^{\mathrm{\prime }}$ with $m_{Z^{\mathrm{\prime }}}\sim 600(12)$GeV and fermionic dark matter with mass $m_{\chi }\sim 50(2000)$GeV, producing excess antiprotons with energies of $\sim 10(300)$GeV. The first model is also compatible with fits for the galactic center GeV gamma-ray excess.