Hidden sector explanation of $B$-decay and cosmic ray anomalies
  There are presently several discrepancies in $b \to s \ell^+ \ell^-$ decays
of $B$ mesons suggesting new physics coupling to $b$ quarks and leptons. We
show that a $Z'$, 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) $Z'$ with $m_{Z'}\sim 600\,(12)\,$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.
