Light Dark Vectors in FCNC Decays

The shift of future physics program from the energy frontier to the intensity frontier will enable probing light dark sectors with very high precision. Light dark vector acts as a minimal portal between the dark and visible sectors and is highly motivated in dark matter model propositions as well as for explanations of discrepancies observed in flavour physics experiments. In this talk I will take you through different light vector boson models and illustrate their fate in context to flavour changing neutral current decays of the B- and K-meson. Contrary to the findings of an earlier work, due to correct calculations of the FCNC amplitudes, we report that O(1) couplings are not required to fit the data on rare and flavour changing B and K decays. We study both on-shell and off-shell phenomenologies of the dark Z decays. Additionally, we also include a robust treatment of hadronic decays of dark Z in its width. However, we find that the allowed parameter region, in spite of providing a very good fit to the b → sl⁺l⁻ data, are ruled out from various other constraints from low energy measurements such as the atomic parity violation, K⁺ → µ⁺ + invisible decay, B_s mixing etc.