Explore the vast range of titles available.

A bstract The cross section of the process e + e − → π + π − has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000 e + e − collider VEPP-2000 in the energy region 525 < s < 883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb − 1 . The systematic uncertainty of the cross section determination is 0.8% at s > 0 . 600 GeV. The ρ meson parameters are obtained as m ρ = 775 . 3 ± 0 . 5 ± 0 . 6 MeV, Γ ρ = 145 . 6 ± 0 . 6 ± 0 . 8 MeV, B ρ → e + e− × B ρ → π + π− = (4 . 89 ± 0 . 02 ± 0 . 04) × 10 − 5 , and the parameters of the e + e − → ω → π + π − process, suppressed by G -parity, as B ω → e + e− × B ω → π + π− = (1 . 32 ± 0 . 06 ± 0 . 02) × 10 − 6 and and ϕ ρω = 110 . 7 ± 1 . 5 ± 1 . 0 degrees.

The SND is a non-magnetic detector deployed at the VEPP-2000 e + e − collider (BINP, Novosibirsk) for hadronic cross-section measurements in the center of mass energy range below 2 GeV. The important part of the detector is a hodoscopic electromagnetic calorimeter (EMC) with three layers of NaI(Tl) counters. EMC signal shaping and digitizing electronics based on FADC allow us to obtain both the energy deposition and the signal arrival time. We demonstrate how EMC time is applied to detect background pileup and cosmic events.

The process e+e-→ηηγ is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb-1 collected by the SND detector at the VEPP-2000 e+e- collider. The e+e-→ηηγ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the ϕη intermediate state. Our result on the e+e-→ηηγ cross section is consistent with the e+e-→ϕη measurement in the ϕ→K+K- mode. The search for radiative processes contributing to the e+e-→ηηγ cross section is performed, and no significant signal is observed.

The process e+e-→nn¯ is studied in the experiment at the VEPP-2000 e+e- collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select nn¯ events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.

The cross section has been measured in the center-of-mass energy range from 1000 to 1060 MeV with the SND detector at the VEPP-2000 electron-positron collider. At the maximum of the (1020) resonance the systematic uncertainty of the cross section measurement is 1.3%, and the statistical uncertainty is 2.2%. To date, this is the most accurate measurement of the cross section. As a result of data approximation with the vector dominance model the decay branching ratio has been measured.

The cross section for the process is measured in the center-of-mass energy region 1.55–2 GeV for integrated luminosity 146 pb collected by the SND detector at the VEPP-2000 collider. The obtained cross section is fitted with the VMD model with and resonances.

Recent results of the SND detector experiments are presented. Data were taken at the VEPP-2000 and the VEPP-2M e+e− colliders in the Novosibirsk in the c.m. energy ranges from 0.3 to 2.00 GeV. Integrated luminosity used are 70pb-1 and 25pb-1 respectively. The cross sections of the e+e− → π0γ, K+K−, ωπ0, π+π−π0η, ωη, ωηπ0 processes has been measured.

New results on exclusive hadron production in e+e− annihilation obtained in experiments with the SND detector at the VEPP-2M and VEPP-2000 e+e− colliders are presented.

The Spherical Neutral Detector (SND) is an experiment for e+e− annihilation study at low energies 0.2−2 GeV. The light quark anti−quark bound states are the main subject of study at these energies. They express themselves as resonances in the e+e− hadronic cross sections. Hadronic cross sections could be recalculated to hadronic vacuum polarization (HVP). The Standard Model predictions today are limited by HVP which is not calculable with modern QCD theory. In this talk we present the review of the hadronic cross sections measurements at SND and new measurements: e+e− → π+π−, π0γ, π+π−π0, ωπ0, K+K−η, η, KsKLπ0, π+π−π0η, ωπ0η e.t.c.

Recent results on e+e−annihilation to hadrons from SND experiment at VEPP-2000 collider are presented. Corresponding data set is about 200 pb−1 of integrated luminosity collected at the energy region below 2 GeV. The processes e+e− → π+π− , π0γ, ωπ0, π+π−π0, ηπ+π−π0, η, π+π−4π0 have been studied. Searches for e+e− annihilation to C-even resonances η and f1(1285) were done.