Discovering 125 GeV techni-dilaton at LHC

Techni-dilaton (TD) is predicted in walking technicolor (WTC) arising as a pseudo NambuGoldstone boson associated with the approximate scale symmetry spontaneously broken by technifermion 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 onedoublet 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.