  Based on lattice simulations using highly improved staggered quarks for
twelve-flavor QCD with several bare fermion masses, we observe a flavor-singlet
scalar state lighter than the pion in the correlators of fermionic
interpolating operators. The same state is also investigated using correlators
of gluonic interpolating operators. Combined with our previous study, that
showed twelve-flavor QCD to be consistent with being in the conformal window,
we infer that the lightness of the scalar state is due to infrared
conformality. This result shed some light on the possibility of a light
composite Higgs boson ("technidilaton") in walking technicolor theories.
