Z-pole test of effective dark matter diboson interactions at the CEPC

Abstract

We investigate the projected sensitivity to effective dark matter (DM)–diboson interaction during the high luminosity Z-pole and 240 GeV runs at the proposed Circular Electron Positron Collider (CEPC). The proposed runs at the 91.2 GeV $$e^+e^-$$ center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the Z boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible Z boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model $$\gamma \bar{\nu }\nu$$ background. Projected sensitivities for the effective $$\gamma Z$$ coupling efficient $$\kappa _{\gamma Z}< (1030\,\hbox {GeV})^{-3}, (1970\,\hbox {GeV})^{-3}$$ for scalar DM, $$\kappa _{\gamma Z}< (360\,\text {GeV})^{-3}, (540\,\text {GeV})^{-3}$$ for fermion DM are obtain for 25 $$\hbox {fb}^{-1}$$ and $$2.5\hbox {ab}^{-1}$$ Z-pole luminosities assuming the optimal low dark matter mass range. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators