At the Large Hadron Collider (LHC), several far detectors such as FASER and MATHUSLA have been proposed to target the long-lived particles (LLPs) featured with displaced vertices. Naturally one question arises as to the feasibility of installing similar far detectors at future lepton colliders like the CEPC and FCC-ee. Because of the different kinematics of final state particles and the...
This talk summarizes a study of realistic design options for a far detector at the Belle II experiment, dubbed GAZELLE. We have quantified the sensitivity of such a detector to long-lived particles produced in e+e- collisions for three benchmark scenarios: axion-like particles, heavy neutral leptons, and a dark matter scenario with a light scalar. GAZELLE will moderately improve the...
As a postron source at the ILC, it is discussed to use pair creation processes by a $\mathcal{O}(\text{MeV})$ photon beam, which is generated from the high-energy electron beam. The current design expects that the photon flux would be as intense as $10^{17}$ photons / s, being the strongest MeV photon source available on the ground.
We propose to use this photon beam for the search for new...
