Zhi-Hui Guo — Page 5

arXiv2008

Resonance sum rules from large $N_C$ and partial wave dispersive analysis

Combining large $N_C$ techniques and partial wave dispersion theory to analyze the $ππ$ scattering, without relying on any explicit resonance lagrangian, some interesting results are derived: (a) a general KSRF relation including the scalar meson contribution; (b) a new relation between resonance couplings, with which we have made an intensive analysis in several specific models; (c) low energy constants in chiral perturbation theory related with $ππ$ scattering in terms of the mass and decay width of resonances.

hep-ph↗

arXiv2007

Is the $f_0(600)$ meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond

O(N) linear $σ$ model is solvable in the large $N$ limit and hence provides a useful theoretical laboratory to test various unitarization approximations. We find that the large $N_c$ limit and the $m_σ\to \infty$ limit do not commute. In order to get the correct large $N_c$ spectrum one has to firstly take the large $N_c$ limit. We argue that the $f_0(600)$ meson may not be described as generated dynamically. On the contrary, it is most appropriately described at the same level as the pions, i.e, both appear explicitly in the effective lagrangian. Actually it is very likely the $σ$ meson responsible for the spontaneous chiral symmetry breaking in a lagrangian with linearly realized chiral symmetry.

hep-ph↗