A. I. Senchenko

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.

Study of the processe+e−→nn¯at the VEPP-2000e+e−collider with the SND detector

The process

Search for the

e^+e^-\to n\bar{n}

\eta^{\prime}\to e^+e^-

has been studied at the VEPP-2000

decay with the SND detector

e^+e^-

Updated measurement of the

collider with the SND detector in the energy range from threshold up to 2 GeV. As a result of the experiment, the

e^+e^- \to \omega \pi^0 \to \pi^0\pi^0\gamma

e^+e^-\to n\bar{n}

cross section with the SND detector

cross section and effective neutron form factor have been measured.

Measurement of the

A search for the process

e^+e^- \to \omega\eta

e^+e^- \to \eta^\prime