Discovering 125 GeV techni-dilaton at LHC

Techni-dilaton (TD) is predicted in walking technicolor (WTC) arising as a pseudo Nambu-Goldstone boson associated with the approximate scale symmetry spontaneously broken by techni-fermion condensation. The TD mass is therefore smaller than those of other techni-hadrons on order of several TeVs, small enough to be within reach of the current LHC search. We present a new method to derive the TD couplings directly from the Ward-Takahashi identities, which enables us to explicitly calculate the quantities relevant to the TD LHC signatures. To set definite benchmarks, we take one-doublet and one-family models of WTC and discuss the TD signatures at LHC, in comparison with those of the standard model (SM) Higgs. It is shown that the TD in the one-doublet model is invisible at the LHC, while the TD signals in the one-family model can be found as a large excess relative to the SM Higgs at around 125 GeV only in the diphoton channel.