Holographic technidilaton

Technidilaton, a pseudo-Nambu-Goldstone boson of scale symmetry, was predicted long ago in the scale-invariant/walking/conformal technicolor (SWC-TC) as a remnant of the (approximate) scale symmetry associated with the conformal fixed point, based on the conformal gauge dynamics of ladder Schwinger-Dyson (SD) equation with nonrunning coupling. We study the technidilaton as a flavor-singlet bound state of technifermions by including the technigluon condensate (tGC) effect into the previous (bottom-up) holographic approach to the SWC-TC, a deformation of the holographic QCD with γm≅0 by large anomalous dimension γm≅1. With including a bulk scalar field corresponding to the gluon condensate, we first improve the operator product expansion of the current correlators so as to reproduce gluonic 1/Q4 term both in QCD and SWC-TC. We find in QCD about 10% (negative) contribution of gluon condensate to the ρ meson mass. We also calculate the oblique electroweak S-parameter in the presence of the effect of the tGC and find that for the fixed value of S the tGC effects dramatically reduce the flavor-singlet scalar (technidilaton) mass MTD (in the unit of Fπ), while the vector and axial-vector masses Mρ and Ma1 are rather insensitive to the tGC, where Fπ is the decay constant of the technipion. If we use the range of values of tGC implied by the ladder SD analysis of the nonperturbative scale anomaly in the large Nf QCD near the conformal window, the phenomenological constraint S≅0.1 predicts the technidilaton mass MTD∼600 GeV which is within reach of LHC discovery.