Long-lived light neutralinos at future Z factories

Future lepton colliders such as the Circular Electron Positron Collider (CEPC) and FCC (Future Circular Collider)-ce would run as high-luminosity Z-boson factories, which offer a unique opportunity to study long-lived particles which couple to Z bosons. In order to exemplify this particular advantage, in this work, we consider one benchmark physics scenario where the long-lived lightest neutralinos pair ((chi) over tilde (0)(1)(chi) over tilde (0)(1)) is produced from Z decays in the context of the R-parity -violating supersymmetry. Our analysis indicates that when assuming BR(Z -> (chi) over tilde (0)(1)(chi) over tilde (0)(1)) = 10(-3) and m((chi) over tilde 10) similar to 40 GeV, the model parameter lambda(112)'/m((f) over tilde)(2) can be discovered down to as low as similar to 1.5 x 10(-14) (3.9 x 10(-14)) GeV-2 at the FCC-ee (CEPC) with center-of-mass energy root s = 91.2 GeV and 150 (16) ab(-1) integrated luminosity. These limits exceed the projected sensitivity reaches of the ATLAS experiment at the high-luminosity Large Hadron Collider (LHC) and the proposed LHC experiments with far detectors (AL3X, CODEX-b, FASER, and MATHUSLA).