Flavor-singlet scalar in large N_f QCD
KMI Science Symposia (ES635)
In the walking technicolor model, the composite flavor-singlet state is regarded as the Higgs-like particle in the real world. While the calculation of the scalar state in the lattice gauge numerical simulation is one of the most challenging subjects, it is important to investigate whether the mass of the scalar state is relatively smaller than the techni-pion decay constant or not, because the experimentally observed mass is smaller than the scalar VEV in the standard model, which is identified (up to O(1) factor) with the techni-pion decay constant in technicolor models. We explain why the calculation is so difficult in the lattice gauge numerical simulation, and how to overcome the problems in our calculation. Furthermore we present encouraging results of the mass of the flavor-singlet scalar in N_f = 12 QCD, where the theory is in the conformal phase, and also in N_f = 8 QCD which might be a candidate of the walking technicolor model.