A. P. Lysenko

The VEPP-2000 electron-positron collider: First experiments

In 2007, at the Institute of Nuclear Physics (Novosibirsk), the construction of the VEPP-2000 electron-positron collider was completed. The first electron beam was injected into the accelerator structure with turned-off solenoids of the final focus. This mode was used to tune all subsystems of the facility and to train the vacuum chamber using synchrotron radiation at electron currents of up to 150 mA. The VEPP-2000 structure with small beta functions and partially turned-on solenoids was used for the first testing of the “round beams” scheme at an energy of 508 MeV. Beam-beam effects were studied in strong-weak and strong-strong modes. Measurements of the beam sizes in both cases showed a dependence corresponding to model predictions for round colliding beams. Using a modernized SND (spherical neutral detector), the first energy calibration of the VEPP-2000 collider was performed by measuring the excitation curve of the phimeson resonance; the phi-meson mass is known with high accuracy from previous experiments at VEEP-2M. In October 2009, a KMD-3 (cryogenic magnetic detector) was installed at the VEPP-2000 facility, and the physics program with both the SND and LMD-3 particle detectors was started in the energy range of 1–1.9 GeV. This first experimental season was completed in summer 2010 with precision energy calibration by resonant depolarization.

Investigation of the processes e+e− → 2 (π+π−π0) and e+e− → 3 (π+π−) with the aid of the CMD-3 detector

The cross sections for the processes e+e− → 2(π+π−π0) and e+e− → 3(π+π−) at c.m. energies in the range of 1.5–2 GeV were measured with the aid of the CMD-3 detector at the VEPP-2000 collider of the Budker Institute of Nuclear Physics (Novosibirsk, Siberian Branch, Russian Academy of Sciences). The integrated luminosity in the respective experiment was 22 pb−1.

Preliminary results of measurements of hadronic cross sections with the CMD-3 detector at the VEPP-2000 electron–positron collider

Experiments with the CMD-3 detector at the VEPP-2000 electron–positron collider in the range of center of mass collision energies from 0.32 to 2 GeV have been performed since December 2010. The amount of accumulated data corresponds to an integrated luminosity of about 60 pb-1. The resultsof a preliminary analysis are presented for the following annihilation channels: e+e- → 3(π+π-), 2(π+π-π0), K+K-π+π-, K+K-,

On the search for the η → e + e − decay at the VEPP-2000 e + e − collider

p\bar p

Measurement of the e + e − → π + π − π 0 cross section with the CMD-3 detector

, and π+π-. Since processes of electron–positron annihilation that involve the production of multihadron states proceed through several intermediate states, their analysis is necessary for the correct description of the emission-angle and invariant-mass distributions of product particles.

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

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.

Controlling the energy of colliding electron-positron beams on the VEPP-2000 accelerator complex

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.

Status and prospects of VEPP-2000 electron-positron collider

We analyze the data on e + e − collisions at c.m.s. energies between 0.32 and 2 GeV collected in 2011–2013 with the CMD3 detector operating at the VEPP-3 e + e − collider of the Budker Institute of Nuclear Physics. The data correspond to an integrated luminosity of nearly 60 pb-1. Preliminary results e + e − → K + K − nπ (n = 1, 2, 3) on the reactions with two charged kaons in the final state are presented, and the procedure for estimating the integrated luminosity for each energy setting is described.