Study of the process e+e−→π+π−π+π−π0 with the CMD-2 detector

Abstract

The process e + e − → π + π − π + π − π 0 has been studied in the center of mass energy range 1280 -1380 MeV using 3.0 pb −1 of data collected with the CMD-2 detector in Novosibirsk. Analysis shows that the cross section of the five pion production is dominated by the contributions of the ηπ + π − and ωπ + π − intermediate states.

Reanalysis of thee+e−→ηγreaction cross section

“…In this approximation the fact that with the free magnitudes and phases of all four ρ, ω, φ, and ρ ′ resonances, the minimized likelihood function has several minima and thus, a choice of the right minimization solution is ambiguous, was ignored. Additional physical restrictions must be applied to, at least, the parameters of the ρ ′ resonance, in order to make a right choice of the minimization solution.In this work the ρ ′ -meson parameters were estimated from the experimental data on the e + e − → ηρ cross section [2,3]. The cross section value in the ρ ′ -resonance maximum obtained from the approximation of the e + e − → ηρ cross section can be translated to the e + e − → ρ ′ → ηγ cross section using VDM as in Ref.…”

“…In this work the ρ ′ -meson parameters were estimated from the experimental data on the e + e − → ηρ cross section [2,3]. The cross section value in the ρ ′ -resonance maximum obtained from the approximation of the e + e − → ηρ cross section can be translated to the e + e − → ρ ′ → ηγ cross section using VDM as in Ref.…”

Review of e+e− → π+π−η

“…[9], in addition to the photon propagation, only the lightest ρ(770) resonance was considered. Comparison with experimental data [1][2][3][4]7] demonstrates fair agreement in the energy region from the ηρ threshold to 1.4 GeV (Fig. 4, left panel).…”

“…Later the process was studied by Orsay (DM2 Collaboration) [2] and Novosibirsk groups (SND, CMD groups) [3,4]. The most recent measurements were performed at the VEPP-2000 collider by the SND group [5] for the CM energy range from 1.22 to 2.00 GeV (the η meson is recontructed via the two-photon mode) and at B-factory with the BaBar detector using the initial state radiation technique [7] in the (1.025; 2.975) GeV CM energy region (the η meson is recontructed via three-pion mode).…”

“…Also data on e + e − → π + π − η can be used to test the conservation of the vector current (CVC) hypothesis. The reaction (1) was first observed at the end of 70's in the DM1 experiment [1] and since that time it was studied by Orsay [2], Novosibirsk [3][4][5][6] groups and by the BaBar collaboration [7,8]. From a theoretical point of view the ηππ production in the e + e − -annihilation and τ-lepton decay was discussed in [4,[9][10][11] using different approaches.…”