π+–π0 mass difference in the Hidden Local Symmetry: a dynamical origin of little Higgs

Masayasu Harada, Masaharu Tanabashi, Koichi Yamawaki
2003 Physics Letters B  
We calculate pi+ pi0 mass difference Δ m_π^2 ≡ m_π^+^2 -m_π^0^2 in the Hidden Local Symmetry (HLS) model, based on the Wilsonian matching and Wilsonian renormalization-group equations. Even without a1 meson the result agrees well with the experiment in sharp contrast to the conventional approach where the a1 meson plays a crucial role. For large Nf QCD, there arises a large hierarchy between Δ m_π^2 and the pi decay constant F_π^2, Δ m_π^2/F_π^2 ≪ 1, near the critical point where the chiral
more » ... etry gets restored as the vector manifestation and the HLS model becomes a little Higgs model with two sites and two links, with the dynamically generated gauge coupling of the composite rho becoming vanishingly small.
doi:10.1016/j.physletb.2003.06.048 fatcat:6kdzhgyotbamrpez4qu6dszcye