Leptophilic Gauge Bosons at Lepton Beam Dump Experiments

It has been recently known that we can use beams of future lepton colliders, the International Linear Collider (ILC), the Compact Linear Collider (CLIC), and the muon collider, for beam dump experiments if a shield and a detector are installed behind the beam dump. We study the prospect of searching for leptophilic gauge bosons (LGBs) in association with $U(1)_{L_e-L_\mu}$, $U(1)_{L_e-L_\tau}$, and $U(1)_{L_\mu-L_\tau}$ gauge symmetries at such lepton beam dump experiments. We perform a detailed calculation of the event rates of the LGB events, taking into account bremsstrahlung and pair-annihilation processes. We show that the lepton beam dump experiments at future lepton colliders can reach parameter regions which are not been covered.