The ratio of the elastic e(+)p to e(-)p scattering cross sections has been measured precisely, allowing the determination of the two-photon exchange contribution to these processes. This neglected ...contribution is believed to be the cause of the discrepancy between the Rosenbluth and polarization transfer methods of measuring the proton electromagnetic form factors. The experiment was performed at the VEPP-3 storage ring at beam energies of 1.6 and 1.0 GeV and at lepton scattering angles between 15° and 105°. The data obtained show evidence of a significant two-photon exchange effect. The results are compared with several theoretical predictions.
Abstract
In this article a short overview of current micro-pattern gaseous detectors development and applications at Budker Institute of Nuclear Physics is presented. The triple-GEM detector for the ...Laser Polarimeter facility and the end-cap discs for the upgrade of the CMD-3 detector are considered in more details.
A method of measurement of the energy of electrons extracted from the VEPP-4M accelerator is described. The method was verified experimentally. The results obtained are in good agreement with ...simulation. The energy resolution is 1.8% for electron energy of 1000 MeV and improves to 0.7% for electron energy of 3500 MeV.
A method for circular e−/e+ accelerator beam energy measurement is proposed. A coordinate of an electron (or a positron) in a focusing magnetic spectrometer built in a circular accelerator depends on ...its energy, two spectrometer parameters, and the circulating beam energy. The spectrometer parameters can be determined using minimum electron energies from Compton backscattering with two laser wavelengths, and a coordinate detector for photons. The photon detector is calibrated separately at well-known beam energy. The VEPP-4M collider has appropriate equipment for the method implementation: built-in focusing magnetic spectrometer, Compton calibration system with two lasers and a photon coordinate detector. Thus, the proposed technique could be implemented with minimum efforts; tests and further upgrade are planned. The beam energy can be defined with expected uncertainty better than 10−4.
The tagging system of the KEDR detector is a symmetrical focusing magnetic spectrometer for electrons and positrons scattered at small angles; it is embedded into the lattice of the VEPP-4M collider ...and intended for two-photon processes study. It measures scattered electron energy with resolution ΔE/E0=0.03% 0.6% (E0 is the beam energy). For precise energy scale calibration two methods are used: tagging of bremsstrahlung electron/positron by the photon energy measured by BGO calorimeter, and direct calibration using Compton backscattering spectrum edge. This report covers design and current status of the calibration system.
The tagging system of the KEDR detector for the two-photon studies is briefly described. The procedure of the energy calibration of the system is considered. Two-photon events e+e− e+e−+μ+μ− selected ...with the central detector were employed to check the energy calibration and to measure the tagging efficiencies. The results obtained demonstrate that the achieved accuracy of the energy calibration is about 1%. To improve the accuracy to the level of 0.3% the upgrade of the calibration system is ongoing. The tagging efficiencies obtained with the simulation agree with the measured one within the error of the measurement.
The present work continues a series of the KEDR measurements of the R value that started in 2010 at the VEPP-4M e+e− collider. By combining new data with our previous results in this energy range we ...measured the values of Ruds and R at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than 2.6% at most of energy points with a systematic uncertainty of about 1.9%. Together with the previous precise R measurement at KEDR in the energy range 1.84–3.05 GeV, it constitutes the most detailed high-precision R measurement near the charmonium production threshold.
Extracted electron and gamma beams in BINP Abramov, G N; Ahmetshin, R R; Barnyakov, A Yu ...
Journal of instrumentation,
08/2014, Letnik:
9, Številka:
8
Journal Article
Recenzirano
Facility of the extracted beams of electrons and gammas based on the e super(+)e super(-) VEPP-4M collider is described. This installation is designed to test prototype of detectors for HEP projects. ...Design parameters of the extracted electron beam are the following: intensity is not less than 50 Hz, energy range is from 0.1 GeV to 3.0 GeV and energy resolution is about 2-3%. The gamma energy range is from 0.05 GeV to 4.0 GeV with an accuracy of 0.5% of energy. The designed intensity of the gamma beam is about 1000 Hz.
Using the KEDR detector at the VEPP-4M e+e− collider, we have determined the values of R at thirteen points of the center-of-mass energy between 1.84 and 3.05 GeV. The achieved accuracy is about or ...better than 3.9% at most of the energy points with a systematic uncertainty less than 2.4%.
KEDR detector has the tagging system (TS) to study the gamma-gamma processes. To determine the two-photon invariant mass, the energies of the scattered at small angles electrons and positrons are ...measured by the magnetic spectrometer embedded into the lattice of the VEPP-4M collider. The energy resolution (scattered electron/positron energy resolution divided by the beam energy) of this spectrometer varies from 0.6% to 0.03% depending on the electron/positron energy. The Compton backscattering of laser radiation on the electron/positron beam is used for the accurate energy scale and resolution calibration of the tagging system. The report covers the design, recent results and current status of the KEDR TS calibration system.
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