Dark Showers with the Z-portal*

We discuss dark shower signals at the LHC from a dark QCD sector, containing GeV-scale dark pions. We consider the Z boson being the main portal between the Standard Model and the dark QCD sector. It can be achieved by integrating out heavy electroweak doublet dark quarks or from the mixing between the Z boson and a dark Z' coupling to the dark quarks. The dark pions decays mediated by the Z boson typically have decay lengths in the range of 1 mm to 10 m. We show that the current displaced di-muon resonance searches at CMS and LHCb can be recasted for the dark showers searches from the Z decay and dark pion searches from FCNC B meson decays, probing parameter regions beyond the bounds from the electroweak precesion measurements and other indirect constraints.