Associated production of neutrino and dark fermion at future lepton colliders

Abstract

Fermionic dark matter can be pairly produced and hence searched with missing energy at colliders. We extend such probe to the associated production of a neutrino and a dark sector fermion at the future e+e− colliders such as CEPC, FCC-ee, ILC, and CLIC. Two typical processes, the mono-photon and electron-positron pair productions associated with missing energy, can serve the purpose. While the mono-photon search prevails at CEPC, FCC-ee, and ILC, the "Image missing" channel has more significant contributions at CLIC with much higher collision energy $$ \sqrt{s} $$ s . The beam polarizations can help further suppressing the SM backgrounds to enhance the signal significance while differential cross sections can distinguish the Lorentz structure of various effective operators. The combined sensitivity can reach well above 1 TeV at CEPC/FCC-ee and ILC while it further touches 30 TeV at CLIC. Comparing with the updated results from the direct detection experiments (XENON1T, PandaX-II, PandaX-4T, LZ, and XENONnT), astrophysical X/γ-ray observations, and cosmological constraints for the sub-MeV absorption dark matter, the collider searches are actually more sensitive and hence can provide a complementary approach to addressing the dark fermions.

Effective Leptophilic WIMPs at the e+e− collider

“…Mono-X, (X ∈ γ, j, Z, H) plus missing energy ( / E) final state is one of the popular probes to search for DM at colliders. The signal of our interest is mono-γ, which has been studied widely at the lepton colliders [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Noticeably, this final state with ISR photon has similar / E event distribution to the huge SM neutrino background (ν νγ), making it difficult for signal-background separation (see supplemental material).…”