Searching for scalar boson decaying into light Z′ boson at collider experiments in U(1)Lμ-Lτ model

We study a model with U(1)(L mu-L tau) gauge symmetry and discuss collider searches for a scalar boson, which breaks U(1)(L mu-L tau) symmetry spontaneously, decaying into light Z ' gauge boson. In this model, the new gauge boson, Z ', with a mass lighter than O(100) MeV, plays a role in explaining the anomalous magnetic moment of muon via one-loop contribution. For the gauge boson to have such a low mass, the scalar boson, phi with O(100) GeV mass appears associated with the symmetry breaking. We investigate experimental constraints on U(1)(L mu-L tau) gauge coupling, kinetic mixing, and mixing between the SM Higgs and phi. Then collider search is discussed considering phi production followed by decay process phi -> Z ' Z ' at the large hadron collider and the international linear collider. We also estimate discovery significance at the linear collider taking into account relevant kinematical cut effects.