Koji Tsumura (National Taiwan University)
We study the feasibility of Type-X two Higgs doublet model (THDM-X) at collider experiments. In THDM-X, new Higgs states are almost decaying into tau leptons. Such scalar bosons are less constrained by current experimental data, because production cross sections are not enhanced by quark Yukawa interaction, and decay products includes multiple missing neutrinos. In this talk, we discuss a search strategy of THDM-X with multi tau lepton final states at ILC and LHC. By using collinear approximation, we show that a four tau signature (e+e- --> AH --> 4tau) can be a clean signal. This talk is based on the paper arXiv:1111.6089.