2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/177453Using 58 million $J/ψ$ events taken with the BES II detector at the Beijing Electron Positron Collider, a new decay mode $J/ψ\toγf_{2}(1270) f_{2}(1270) \to γπ^+π^-π^+π^-$ is observed for the first time. The branching ratio is determined to be $Br(J/ψ\toγf_{2}(1270) f_{2}(1270))=(9.5\pm0.7\pm1.6)\times 10^{-4}$, where the quoted errors are statistical and systematic, respectively.7 pages, 3 figuresHigh Energy Physics - Experimenttext