E. V. Pakhtusova

Electromagnetic Pion Form-Factor in the Timelike Region

Abstract The pion electromagnetic form factor has been measured at the VEPP-2M collider in the c.m. energy range 360 MeV–1400 MeV with the detectors OLYA and CMD. On the basis of all available data for the pion form factor collected in the timelike region, the following values for ρ-meson parameters were obtained: m ρ = 775.9 ± 1.1 MeV, σ ρ = 150.5 ± 3.0 MeV. The ω-meson branching ratio into π + π − pair, electromagnetic radius of the pion, ππ scattering length in the P-wave and the strong interaction contribution to the muon ( g − 2) value were found to be B ωππ = (2.3 ± 0.4)%, 〈 r π 2 〉 = 0.422 ± 0.013 fm 2 , a 1 1 = 0.033 ± 0.033m π −3 , a H = (68.4 ± 1.1) × 10 −9 .

Summary of experiments with the neutral detector at the e+e− storage ring VEPP-2M

Abstract The complete results of the experiments carried out with the Neutral Detector at the e + e − storage ring VEPP-2M in the energy range 2 E =0.5–1.4 GeV are reviewed. The data sample corresponds to a total integrated luminosity of 19 pb −1 .

Spherical neutral detector for VEPP-2M collider

The Spherical Neutral Detector (SND) operates at VEPP-2M collider in Novosibirsk studying e^+e^- annihilation in the energy range up to 1.4 GeV. Detector consists of a fine granulated spherical scintillation calorimeter with 1632 NaI(Tl) crystals, two cylindrical drift chambers with 10 layers of sense wires, and a muon system made of streamer tubes and plastic scintillation counters. The detector design, performance, data acquisition and processing are described.

Update of the e+e− → π+π− cross section measured by the spherical neutral detector in the energy region 400 < √s < 1000 MeV

The corrected cross section of the e^+e^-\to\pi^+\pi^- process measured in the SND experiment at the VEPP-2M e^+e^- collider is presented. The update is necessary due to a flaw in the e^+e^-\to\pi^+\pi^- and e^+e^-\to\mu^+\mu^- Monte Carlo events generators used previously in data analysis.The corrected cross section of the e^+e^-\to\pi^+\pi^- process measured in the SND experiment at the VEPP-2M e^+e^- collider is presented. The update is necessary due to a flaw in the e^+e^-\to\pi^+\pi^- and e^+e^-\to\mu^+\mu^- Monte Carlo events generators used previously in data analysis.The corrected cross section of the e+e− → π+π− process measured in the spherical neutral detector experiment at the VEPP-2M e+e− collider is presented. The update is necessary due to a flaw in the e+e− → π+π− and e+e− → μ+μ− Monte Carlo event generators used previously in data analysis.

First observation of φ(1020)→π0π0γ decay

In the SND experiment at the VEPP-2M electron-positron collider the PHI(1020)--->PI0+PI0+GAMMA decay was studied. The branching ratio B(PHI--->PI0+PI0+GAMMA)=(1.14+-0.10+-0.12)x10^{-4} was measured. It was shown, that the F0(980)GAMMA mechanism dominates in this decay and the 4-quark model of F0(980) describes our data most consistently.Abstract In the SND experiment at VEPP-2M e + e − collider the φ (1020)→ π 0 π 0 γ decay was studied. Its branching ratio B ( φ → π 0 π 0 γ )=(1.14±0.10±0.12)·10 −4 was measured. It was shown, that f 0 (980) γ mechanism dominates in this decay. Corresponding branching ratio B ( φ → f 0 γ )=(3.42±0.30±0.36)·10 −4 was obtained.

The φ(1020) → π0π0γ decay

In the SND experiment at VEPP-2M

Study of the process e+e− → π+π− in the energy region \(400 < \sqrt s < 1000 MeV^\P \)

e^+e^-

Measurements of the parameters of the

collider the

\phi(1020)

\phi(1020)\to\pi^0\pi^0\gamma

resonance through studies of the processes

decay was studied and its branching ratio was measured: