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 <$$ \sqrt{s} $$
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 $$ \sqrt{s} $$
s
> 0.600 GeV. The ρ meson parameters are obtained as mρ = 775.3 ± 0.5 ± 0.6 MeV, Γρ = 145.6 ± 0.6 ± 0.8 MeV, Bρ→e+e− × Bρ→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 Bω→e+e− × Bω→π+π− = (1.32 ± 0.06 ± 0.02) × 10−6 and and ϕρω = 110.7 ± 1.5 ± 1.0 degrees.
The results of a search for direct production of the f 1 (1285) resonance in e + e − annihilation are presented. The analysis is based on data with an integrated luminosity of 15.1 pb −1 accumulated in the experiment with the SND detector at the VEPP-2000 e + e − collider in the center-of-mass energy range 1.2 − 1.4 GeV. Two e + e − → f 1 (1285) candidate events are found at the peak of the resonance and zero events beyond the resonance. The significance of the e + e − → f 1 (1285) signal is 2.7σ. The cross section at the maximum of the resonance is found to be σ(e + e − → f 1 ) = 54 +32 −23 pb. The corresponding branching fraction B(f 1 (1285) → e + e − ) = (6.1 +3.6 −2.6 ) × 10 −9 .We consider this result as a first indication of the process e + e − → f 1 (1285). The measured branching fraction is consistent with the theoretical prediction.
A search for the rare decay η → e + e − is performed using the inverse process e + e − → η in the decay mode η → π 0 π 0 π 0 . We analyze data with an integrated luminosity of 654 nb −1 accumulated at the VEPP-2000 e + e − collider with the SND detector at the center-of-mass energy E = m η c 2 ≈ 548 MeV, and set the upper limit B(η → e + e − ) < 7 × 10 −7 at the 90% confidence level.
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.
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