S.A. Nikitin

A high precision measurement of the ϒ, ϒ′ and ϒ″-meson masses

Abstract An experiment has been performed at the storage ring VEPP-4 using the MD-1 detector. The resonance depolarization method has been employed for the absolute calibration of the beam energy. This has allowed the accuracy of the mass measurement to be improved by a factor of ten. The following mass values of ϒ, ϒ′ and ϒ″ -mesons have been obtained: M ( ϒ )=9460.6±0.4 MeV, M ( ϒ ′)=10023.8±0.5 MeV, M ( ϒ ″)=10355.5±0.5 MeV.

Large impact parameter cut-off in the process e+e−→e+e−γ

Abstract In investigating the e + e − → e + e − γ process the radiation probability is oberved to be substantially less than that calculated in the standard QED. The effect is due to the fact that the characteristic impact parameters in the process are much greater than the transverse sizes of the colliding beams. The Compton scattering γ-spectrum of the synchrotron radiation by a colliding beam is measured.

Absolute calibration of particle energy at VEPP-4M

We have started a new series of experiments on a precise measurement of J/Ψ-, Ψ′- mesons and τ-lepton masses at VEPP-4M collider with KEDR detector. Features of the method used for an absolute particle energy calibration based on the resonance depolarization are described.

Experiments on the physics of charged particle beams at the VEPP-4M electron-positron collider

The VEPP-4M accelerator facility with a universal KEDR detector is designed to conduct experiments with colliding electron-positron beams. High-energy physics, nuclear physics, and studies using synchrotron radiation are the main directions of research with this facility. In addition, experiments on poorly explored issues in the physics of beams in the electron-positron storage ring and methodological studies to prepare an experiment aimed at testing corollaries of the CPT theorem for an electron and a positron are regularly conducted at the VEPP-4 facility. A number of works performed in recent years are described: studies to increase the accuracy of comparing the electron and positron spin precession frequencies by the resonant depolarization method; measurements of the count rate of Touschek electrons as a function of the beam energy in a wide range; comparison of the methods for measuring the beam energy spread; a study of the electron beam dynamics when a nonlinear betatron resonance is crossed.

A high precision measurement of the υ-meson mass

Abstract A high precision measurement of the υ-meson mass has been performed at the storage ring VEPP-4 using the MD-1 detector. The resonance depolarization method has been used for the absolute calibration of the beam energy that allowed to improve the accuracy of υ-mass measurement by a factor of ten. The following mass value has been obtained: M = 9459.7 ± 0.6 MeV.

Calculation of the intensity of Touschek electrons in the VEPP-4M storage ring

Formulas for calculating the intensity of intrabeam scattering of electrons in the Born approximation for the one- and two-dimensional collision models have been obtained for the nonrelativistic and relativistic cases. The Baier-Katkov-Strakhovenko two-dimensional relativistic model with Coulomb corrections has been analyzed. Formulas in the ultrarelativistic limit have been obtained using this model. Different models have been compared. The intensities of Touschek electrons and the polarization contribution have been calculated under the conditions of the detection of scattered particles at the VEPP-4M storage ring. The calculations have been compared to experimental data.

3D PIC method development for simulation of Beam-Beam effects in supercolliders

A new Beam-Beam simulation code based on a 3D PIC method has been developed. Taking into account to the full extent the three-dimensional nature of interaction can be useful for studies of a pinch effect at large crossing angles in ILC and Crab Waist properties in SuperB Factory. The numerical examples of the electron and positron bunches movement and collision simulation are presented.

Application of internal gas target for beam polarization measurement in the electron storage ring

First results on polarization measurement are presented. More sophisticated scheme of polarimeter is proposed. It is expected that the accuracy of the measurement of polarization of the circulated electron beam of about 20% will be achieved during 8 minutes of operation of this Moller polarimeter. The work was supported by Russian Foundation for Basic Researches, grants 98-02-17949 and 98-02-17993, INTAS, grant 96-0424 and State Scientific and Technical Programm (Nuclear Physics).

Precise Energy Measurements in Experiments on VEPP-4M Collider

The series of experiments on mass measurements of J/Ψ, Ψ ψ, ψ′, X and D mesons have been done on VEPP4-M collider. The accuracy of obtained masses values for Ψ mesons exceeded world value more than 3 times. Experiment on mass measurement of tau lepton is in progress. All these experiments require absolute energy calibration of the beams. Resonant depolarization technique has been used for most accurate energy measurement with relative accuracy of 1 ppm (10-6). Compton backscattering effect is used in developing facility for fast energy measurements. Möller scattering of the beam on polarized gas jet target has been used for beam polarization measurements.

High Precision Measurement of the

Abstract A high precision measurement of the υ-meson mass has been performed at the storage ring VEPP-4 using the MD-1 detector. The resonance depolarization method has been used for the absolute calibration of the beam energy that allowed to improve the accuracy of υ-mass measurement by a factor of ten. The following mass value has been obtained: M = 9459.7 ± 0.6 MeV.