VEPP-2000 is an electron-positron collider with round beams built and operating at the Budker Institute of Nuclear Physics. The integrated luminosity accumulated over last 2 years has reached 0.5 fb–1 with peak luminosity of 0.9 × 1032 cm–2 s–1. The short description of the VEPP-2000 complex and current status with achieved results are presented.

The VEPP-5 injection complex is a source of electron and positron beams for the VEPP-2000 and VEPP-4 complexes and is considered as an injector for the future collider project. The performance of the complex is sufficient for current users, but needs to be improved to serve future setups. Work is underway at the injection complex to improve the stability of operation and ease of use. Current achievements and planned improvements of the injection complex are described.

The cross section of the process e+e- -> x-+x-- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb-1. In the dominant p-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around 0-resonance the x-+x-- production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the x-+x-- production has also been measured. It shows a strong deviation from the theoretical prediction based on the conventional scalar quantum electrodynamics framework, and it is in good agreement with the generalized vector-meson-dominance and dispersive-based predictions. The impact of the presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.

Results are presented from measuring the e^+e^-→ nn̅ cross section and effective neutron timelike form factor. Data are collected in 2020–2021 at the VEPP-2000 e^+e^- collider in the 1891 to 2007 MeV center-of-mass range of energies. The general purpose nonmagnetic SND detector is used to detect neutron–antineutron events. The time-of-flight approach is used to select nn̅ events. The measured cross section is 0.4–0.6 nbn. The neutron form factor in the investigated range of energies varies from 0.3 to 0.2.

The process e^+e^-→π^+π^-π^0 was studied in the energy range between 1.075 and 1.975 GeV on the basis of data characterized by an integrated luminosity of about 70 pb ^-1 that were accumulated in an experiment with the Spherical Neutral Detector (SND) at the VEPP-2000 e^+e^- collider. The respective Dalitz distributions were analyzed within a model that includes ρ(770)π , ρ(1450)π , and ωπ^0 intermediate states. As a result, the energy dependences of the total cross section for the process e^+e^-→π^+π^-π^0 and the cross sections for the ρ(770)π and ρ(1450)π intermediate states were measured along with the phase shift of the ρ(770)π amplitude with respect to the ρ(1450)π and ωπ^0 amplitudes. For the first time, a simultaneous approximation of the cross sections for the processes e^+e^-→ρ(770)π and ρ(1450)π and the relative phase of the respective final states was performed on the basis of the vector-meson dominance model. The contributions of the ω , ϕ , ω(1420) , and ω(1650) resonances were taken into account. The approximation showed that the decay ω(1650)→π^+π^-π^0 proceeds predominantly through the ρ(1450)π intermediate state, while the decay ω(1420)→π^+π^-π^0 receives a dominant contribution from the ρ(770)π mechanism. The results of this study refined the results of earlier measurements with the SND setup.

The cross section of the process $e^+e^-\to\pi^+\pi^-$ has been measured in the center-of-mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on an integrated luminosity of about 88 pb$^{-1}$, of which 62 pb$^{-1}$ represent a complete dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near the $\rho$ resonance a systematic uncertainty of 0.7% was achieved. The implications of the presented results for the evaluation of the hadronic contribution to the anomalous magnetic moment of the muon are discussed.

The conversion decay w® p0e+e- with the CMD-3 detector on the VEPP-2000 electron-positron collider VEPP-2000 at the Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences was investigated. The data from the first scan were used in the work, which corresponded to an integral brightness of around 10 pb–1 in the energy range of 660 to 840 MeV in the center of mass system. The 1113 ± 37 signal events were detected. The product of the relative decay probability and ω-meson width G(w® e+e- ) × Br(w® p0e+e- ) = (4, 20 ± 0,12 ± 0, 25) ×10-7 MeV, as well branching ratio Br(w® p0e+e- ) = (6, 78 ± 0,19 ± 0, 40) ×10-4 are measured with better precision than the world average.

The VEPP-5 injection complex is a source of intense electron and positron beams that supplies the VEPP-4M and VEPP-2000 accelerator complexes through the K-500 transport channel. At present, the injection complex is in regular operation. Work is being carried out to improve the performance and stability of the facility, and possible ways of working with perspective beam users are being considered. This article presents a description of the injection complex and the experience of its operation, as well as the latest improvements being considered.

We present the study of the decay J/ψ → ρπ . The results are based on of 5.2 million J/ψ events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured to be ℬ ( J/ψ → ρπ ) = (2 . 072 ± 0 . 017 ± 0 . 062) ∙ 10 − 2 and ℬ ( J/ψ → π + π − π 0 ) = (1 . 878 ± 0 . 013 ± 0 . 051) ∙ 10 − 2 , where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.

A cross section of the process e+e−→KS0K±π∓π+π− has been measured for the first time using a data sample of 185.4 pb−1 collected with the CMD-3 detector at the VEPP-2000 e+e− collider. With the KS0→π+π− decay detection, 373±20 and 514±28 signal events have been selected with six and five reconstructed tracks, respectively, in the center-of-mass energy range 1.6–2.0 GeV. The total systematic uncertainty of the cross section is about 15%. A study of the production dynamics allows us to extract a contribution from the e+e−→f1(1285)π+π− intermediate state and to measure the corresponding cross section. The intermediate states with the f1(1420) and f1(1510) resonances have been observed.

The VEPP-2000 is an electron–positron collider with round beams built and operating at the Budker Institute of Nuclear Physics (BINP). The collider luminosity was increased twofold last year. The integrated luminosity accumulated over the last year has exceeded 0.3 fb –1 , which almost doubled the total data collected since the collider operation began. The short description of the VEPP-2000 complex, current status, and the results are presented in this work.

The process $e^+e^- \to \omega\pi^0 \to \pi^+\pi^-\pi^0\pi^0$ is studied in the center-of-mass energy region $1.05-2.00$ GeV using data with an integral luminosity of about 35 pb$^{-1}$ collected with the SND detector at the VEPP-2000 $e^+e^-$ collider. In the energy range under study, the value of the measured Born cross section varies from 0.7 to 18 nb. The statistical uncertainty of the cross section is $2-23$%, while the systematic uncertainty is in the range of $3.0-14.2$%. The results are consistent with previous measurements but have better accuracy.

A cross section of the process e+e−→KS0K±π∓π+π− has been measured for the first time using a data sample of 185.4 pb−1 collected with the CMD-3 detector at the VEPP-2000 e+e− collider. With the KS0→π+π− decay detection, 373±20 and 514±28 signal events have been selected with six and five reconstructed tracks, respectively, in the center-of-mass energy range 1.6–2.0 GeV. The total systematic uncertainty of the cross section is about 15%. A study of the production dynamics allows us to extract a contribution from the e+e−→f1(1285)π+π− intermediate state and to measure the corresponding cross section. The intermediate states with the f1(1420) and f1(1510) resonances have been observed.

The collective beam instabilities in the damping ring of the VEPP-5 injection complex have been investigated. Wakefields created by the charged-particle beam distort the potential well of the accelerating RF system, which leads to beam lengthening and to distortion of the shape of its longitudinal distribution. The longitudinal beam profile has been measured by a dissector and a streak camera, and the process of potential well distortion of the RF system is theoretically justified. A model of the coupling impedance in the form of an equivalent RLC circuit has been constructed, and its parameters are estimated by comparing the simulation data to experimental results. The obtained model of the coupling impedance has been used to predict the behavior of the damping ring beam after modification of the accelerator vacuum system.

AbstractThe process $$e^+e^-\rightarrow n{\bar{n}}$$ e + e - → n n ¯ is studied in the experiment at the VEPP-2000 $$e^+e^-$$ e + e - collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select $$n{\bar{n}}$$ n n ¯ 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 process $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb $$^{-1}$$ - 1 collected by the SND detector at the VEPP-2000 $$e^+e^-$$ e + e - collider. The $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\phi \eta $$ ϕ η intermediate state. Our result on the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is consistent with the $$e^+e^-\rightarrow \phi \eta $$ e + e - → ϕ η measurement in the $$\phi \rightarrow K^+ K^-$$ ϕ → K + K - mode. The search for radiative processes contributing to the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is performed, and no significant signal is observed.

The process e^+e^-→ nn̅ 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 nn̅ 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.

We review the recent results obtained by the KEDR experiment in the charmonium energy range. They include the measurements of J/psi meson total and partial widths and exclusive branching fractions, study of D+ and D-0 meson masses and R between 1.8 and 7.0 GeV.

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 < $$ \sqrt{s} $$ 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 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.