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 2.5hbox {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.