Observation of the φ→π+π−π+π− decay

AbstractUsing 11.6 pb −1 of data collected in the energy range 0.984–1.06GeV by CMD-2 at VEPP-2M, the cross section of the reaction e + e − →π + π − π + π − hasbeen studied. For the firsttime an interference patternwas observed in the energy dependence of the cross section near theφ meson. The branching ratio of the φ → π + π − π + π − decay doublesuppressed by the G-parity and OZI rule is measuredBr(φ → π + π − π + π − ) = (3.93 ±1.74 ±2.14) ·10 −6 .The upper limits have been placed for the decays φ → π + π − π + π − π 0 and φ → ηπ + π − Br(φ → π + π − π + π − π 0 ) < 4.6 ·10 −6 90%CL,Br(φ → ηπ + π − ) < 1.8 ·10 −5 90%CL. 1 Introduction Production of four pions in e + e − annihilation is now well studied in the c.m.energy range 1.05 to 2.5 GeV (see [ 1] and references therein). Results onthe measurements of the cross section of the reaction e + e − → π + π − π + π − in the energy range from 0.60 to 0.97 GeV as well as the probability of theρ 0 meson decay into the π + π − π + π −