K. I. Beloborodov

Study of the e + e – → π+π–π0 process in the energy range 1.05–2.00 GeV

The cross section for the e+e– → π+π–π0 process in the energy range 1.05–2.00 GeV has been measured using the data collected in the experiment with the Spherical Neutral Detector (SND) at the VEPP-2000 e+e– collider. The obtained results on the cross section are in good agreement with previous measurements by the SND at the VEPP-2M collider and BABAR, but have a better accuracy.

Testing aerogel Cherenkov counters with n = 1.05 using electrons and muons

A system of threshold aerogel Cherenkov counters with refractive index n = 1.05 has been tested. This system has been designed for e/π separation with energies of up to 450 MeV in experiments aimed at measuring cross sections of e+e−-annihilation into hadrons with the SND detector at the VEPP-2000 collider. The characteristics of the system are presented. The measurements have been taken using electrons and muons from e+e− → e+e− and e+e− → μ+μ− reactions at beam energies of 250–500 MeV. If the mean signal from electrons in the counter is 3.5 photoelectrons, the detection efficiency for electrons is 0.955.

Measurement of the e+e− → ηπ+π− cross section in the \sqrt s = 1.04–1.38-GeV energy range with a spherical neutral detector at the VEPP-2M collider

AbstractThe e+e− → ηπ+π− cross section in the η → 2γ channel has been measured in the

Measurement of the cross section for the e + e − → ωπ0 → π0π0γ process in the energy range of 1.1–1.9 GeV

nsqrt s n

Measurement of the ω, ρ → π0e+e− branching fractions

= 1.04- to 1.38-GeV energy range. The data with a total integrated luminosity of 9.05 pb−1 were collected on a spherical neutral detector at the VEPP-2M collider. The results are consistent with the BaBar and CMD2 data and have a higher statistical accuracy.

New results of measurement of cross sections for electron-positron annihilation to hadrons with the SND detector at VEPP-2000

The sensitivity of the VEPP-2000 e+e− collider in the search for the rare decay η → e+e− has been studied. The inverse reaction e+e− → η is proposed for this search. We have analyzed a data sample with an integrated luminosity of 108 nb−1 collected with the SND detector in the center-of-mass energy range 520–580 MeV and found no background events for the reaction e+e− → η in the decay mode η → π0π0π0. In the absence of background, a sensitivity to B(η → e+e−) of 10−6 can be reached during two weeks of VEPP-2000 operation. Such a sensitivity is higher than the current upper limit on B(η → e+e−) by a factor of 2.3.

Search for the e + e − → K ± K S π ∓ process on the VEPP-2M e + e − collider

The cross section for the e+e− → ωπ0 → π0π0γ process has been measured in the energy range of 1.1–1.9 GeV. The measurement has been made with the Spherical Neutral Detector at the VEPP-2000 e+e− collider. The data in the energy range of 1.1–1.4 GeV are in agreement with the earlier measurements with the SND and CMD-2 detectors. The cross section has also been measured above 1.4 GeV.

Search for e + e − → f 0 (600)γ, f 0 (980)γ, f 0 (1350)γ, and f 2 (1270)γ processes in the energy range from 1.05 to 1.38 GeV

The cross section for the process e+e− → π+π−π0π0 has been measured in an experiment with a spherical neutral detector, with the cross section at energies √s < 920 MeV having been measured for the first time. The model of vector dominance describes well the data obtained if the ρ, ρ′, and ρ″ resonances are taken into account. The probability of the decay ρ → π+π−π0π0 is B(ρ → π+π−π0π0) = (1.60 ± 0.74 ± 0.18) × 10−5. The upper limit for the decay ω → π+π−π0π0 has been improved by two orders of magnitude compared to previous measurements and is B(ω → π+π−π0π0) < 2 × 10−4 at a 90% confidence level.