2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42247We improve $O(p^4)$ calculation in $U(2)_L\times U(2)_R$ chiral theory of mesons by resummation calculation for vector mesons physics and restudy decay $ρ\toππ$. A complete and compact expression for $f_{ρππ}(p^2)$ (up to $O(p^\infty)$) is obtained, from which an important non-perturbative conclusion is given based on convergence and unitarity consideration.5 pages, 2 figuresHigh Energy Physics - Phenomenologytext