VEPP-2000 Collider Research Articles

Search for the process e+e−→η′γ in the energy range s=1.075−2 GeV

The results of the search for the e+e−→η′γ process in the center-of-mass energy range from 1.075 to 2 GeV are presented. We analyze data with an integral luminosity of 746 pb−1 accumulated with the SND detector at the e+e− collider VEPP-2000 in 2010–2024. The η′→ηπ0π0 decay is used in the analysis, with the subsequent η and π0 decays into γγ. Upper limits not exceeding 13 pb have been set on the e+e−→η′γ cross section at the 90% confidence level. Published by the American Physical Society 2024

Development of Digital Signal Processing Techniques with BPM

In order to ensure the continuity of operation of the VEPP-2000 collider, accurate measurement of the betatron frequency is necessary. To do this, this work proposes to use methods that refine the Fourier transform, such as parabola interpolation (Gassior method), NAFF and window functions. The refined frequency is subsequently used in construction of phase portraits of the beam to control the interference of high-order magnetic fields. In addition, the work discusses methods for extracting a signal from a mixture for subsequent analysis – PCA and ICA. Finally, to improve the accuracy of frequency determination, the paper considers the simplest implementation of a Kalman filter to improve the accuracy of subsequent harmonic analysis. In addition to all of the above, the paper briefly discusses a method for monitoring the operation of the beam position monitors themselves.

Measurement of the e+e−→π+π− cross section from threshold to 1.2 GeV with the CMD-3 detector

The cross section of the process e+e−→π+π− 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 ρ-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around ϕ-resonance the π+π− production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the π+π− 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. Published by the American Physical Society 2024

Measurement of the Pion Form Factor with CMD-3 Detector and Its Implication to the Hadronic Contribution to Muon (g-2).

The cross section of the process e^{+}e^{-}→π^{+}π^{-} has been measured in the center-of-mass energy range from 0.32 to 1.2GeV 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 1GeV. In the dominant region near the ρ 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.

Non-Destructive Single-Revolution Electron Beam Profilometer based on a CCD Camera

CCD cameras are easy to use and are quite widespread in the optical diagnostics of beams in particle accelerators. The exposure time of these cameras is milliseconds, so they are usually used in a cumulative mode to monitor the circulating beams. The images from the cameras contain information about the transverse distribution of particles in the beam and the position of the center of mass of the beam. In this paper, using the example of CCD cameras installed on the electron-positron collider VEPP-2000, the possibility of their use in the mode of a single beam flight through the observation site is investigated. The intensity of the luminous flux of the optical part of the synchrotron radiation spectrum of the beam was estimated and an image of the transverse distribution of particles in the beam in a single-span mode was experimentally obtained, which confirms the potential for expanding the scope of this diagnostic system. A trial signal processing was done as a demonstration of the determination of the beam parameters by the method under study.

The first measurement of the conversion decay of the omega meson into a neutral pion and an electron-positron pair at the CMD-3 detector

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.

Analysis of the CMD-3 detector data: selection of low-energy electron-positron annihilation into KKππ0

We explore the process e+e− → KSK+-π−+π0 with the CMD-3 detector at the electron-positron collider VEPP-2000. Here, we present a selection algorithm. The data amassed by the CMD-3 detector in the energy range of 1.2–2 GeV during 2011, 2012, 2017, 2019 runs, with a total luminosity integral of ∼120pb−1 backs the analysis. Two reasons stand behind the study. First, a recent report of anomalous magnetic moment discrepancy broadening to 4.2σ, see Fermilab article [1]. Searching for New Physics demand sharper Hadronic Vacuum Polarization (HVP) estimate. In its turn, HVP computation relies heavily on hadronic cross-sections measurement. Second, an intermediate vector resonance near 2 GeV (ϕ’’) is still a mystery. It might be a state, or a hybrid , or ΛΛ− state. Untangling partial decay widths, measuring isospin 1 and 0 cross-sections for e+e− → KSK+-π−+π0, might discern between different ϕ’’ models.

Recent SND experiment results on e+e− annihilation to hadrons

We review here recent results on [Formula: see text] annihilation to hadrons below 2 GeV obtained with the SND detector at the VEPP-2000 collider. Among others we report cross sections and dynamics properties for the [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].

The measurement of the omega meson parameters with the CMD-3 detector at the electron-positron collider VEPP-2000

The cross section of the process e+ e– → π+ π– π0 was measured with the CMD-3 detector at the electron-positron collider VEPP-2000 in the ω meson energy region based on the data collected in 2013–2018 and corresponding to an integrated luminosity of 40 pb–1. The parameters of the ω-meson: Mω = 782.67 ± 0.01 ± 0.1 MeV, Γω = 8.56 ± 0.02 ± 0.07 MeV, σ0(ω → π+ π– π) = 1629 ± 3 ± 36 nb with the precision match or even exceeding the previous data are obtained.

Recent results on e +e − annihilation to hadrons in the SND experiment

Recent results of the SND experiment at the VEPP-2000 collider on e +e − annihilation to hadrons below 2 GeV are presented. In particular, we discuss measurements of the e +e − → π +π − and e +e − → nn¯ cross sections. The processes e +e − → π +π −π 0 , K+K−π 0 , ηπ0 γ and 2ηγ were under investigation as well. The preliminary results on the e +e − → ωπ0 → π +π −2π 0 cross section measurement are also presented.

Upgrade of the CMD-3 trigger system

In 2017, the luminosity at the VEPP-2000 collider at the Budker Institute of Nuclear Physics SB RAS, Novosibirsk, was increased. This required an upgrade of the L-1 trigger to improve system performance and stability while reducing latency. In addition, the existing L-1 trigger firmware blocks are outdated and do not meet the new requirements. For this, the development of a device called the decision block will be created. The task of this unit is to generate the decision on whether to record the current event. In this paper, we present the stages of upgrading the L-1 trigger, the decision block design and implementation.

Overview of Recent Results from the SND Experiment at the VEPP-2000 Collider

Overview of Recent Results from the SND Experiment at the VEPP-2000 Collider

Nonlinear Coupling Resonances in X-Y Coupled Betatron Oscillations Near the Main Coupling Resonance in VEPP-2000 Collider

Nonlinear Coupling Resonances in X-Y Coupled Betatron Oscillations Near the Main Coupling Resonance in VEPP-2000 Collider

Two-Stream Effects in Coherent Beam-Beam Oscillations in VEPP-2000 Collider Near the Linear Coupling Resonance

Two-Stream Effects in Coherent Beam-Beam Oscillations in VEPP-2000 Collider Near the Linear Coupling Resonance

Measurement of the e+e\u2212 \u2192 \u03c0+\u03c0\u2212 process cross section with the SND detector at the VEPP-2000 collider in the energy region 0.525 < sqrt{s} < 0.883 GeV

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} < 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} > 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.

Study of the process e + e– → π+ π– π0 with the CMD-3 detector at the electron-positron collider VEPP-2000

The cross section of the process e+ e– → π+ π– π0 was measured with the CMD-3 detector at the electron-positron collider VEPP-2000 in the energy region from 750 MeV to 800 MeV in c.m.s. This measurement was based on the data collected in 2013 and related to an integrated luminosity of about 7.8 pb–1. The procedure for obtaining the Born cross section and determining the parameters of the ω-meson was worked out. The preliminary ω-meson parameters mω = 782.70 ± 0.02 ± ± 0.11 MeV, Гω = 8.74 ± 0.05 ± 0.22 MeV, σ0(ω → π+ π– π) = 1545 ± 4 ± 39 nb were obtained. The results were compared with previous data and proven to demonstrate a good agreement with them.

The CMD-3 detector's Final Decision Block

In 2017, the luminosity at the VEPP-2000 collider at the Budker Institute of Nuclear Physics SB RAS, Novosibirsk, was increased. In this regard, it was decided to upgrade the trigger system of the CMD-3 detector. For this, the development of a device called the Final Decision Block was started. The task of this unit is to generate the final decision on recording the current event in the detector based on the data received from the Charged and Neutral triggers. In this paper, we present the designed block and tests carried out with it, as well as its integration in the Data Acquisition System of the CMD-3 detector. The test results are presented both at the test bench and directly as a part of the Data Acquisition System of the detector.

Study of the process e+e− → KSK±π∓ with CMD-3 detector

A recent result of the cross section measurement of the process at collider VEPP-2000 is presented using a data sample of the ∼150 pb−1 integrated luminosity collected with the CMD-3 detector. The processes with charged kaons in multi hadron events attract special interest, because they impact strongly on studies of light quark hadronization, isospin symmetry, and strange meson spectroscopy. Experimental results of cross section are presented in a broad energy range covered by the VEPP-2000 and compared to earlier measurements. A study of the production dynamics confirms the dominance of neutral intermediate state.

DQM Tools and Techniques of the SND Detector

SND detector operates at the VEPP-2000 collider (BINP, Novosibirsk). To improve events selection for physical analysis and facilitate online detector control we developed new data quality monitoring (DQM) system. The system includes online and reprocess control modules, automatic decision making scripts, interactive (web based) and program (python) access to various quality estimates. This access is implemented with node.js server with data in RDBMS MySQL. We describe here general system logics, its components and some implementation details.

Current Status and Planned Upgrades of the VEPP-5 Injection Complex

The VEPP-5 injection complex, consisting of two linacs and a damping storage ring, delivers electron and positron beams to the VEPP-4M and VEPP-2000 colliders operating at BINP. Over three years of injector operation, its efficiency has significantly increased and the maximum positron-storage rate has reached 1.2 × 1010 s–1. This progress was reached through tuning the constituent machines, upgrading the accelerator technology, and deploying a new 11-MHz station of RF cavities. By the start of the next running season, a new electron gun with a significantly increased maximum current and cathode lifetime will be installed.