V. S. Bobrovnikov

Measurement of main parameters of the ψ(2S) resonance

A high-precision determination of the main parameters of th eψ(2S ) resonance has been performed with the KEDR detector at the VEPP-4Me+e− collider in three scans of the ψ(2S )–ψ(3770) energy range. Fitting the energy dependence of the mu ltihadron cross section in the vicinity of theψ(2S ) we obtainedthe mass value M = 3686.114± 0.007± 0.011 +0.002 −0.012 MeV and the product of the electron partial width by the branchin g fraction into hadrons Γee × Bh = 2.233± 0.015± 0.037± 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference e ffects in the cross section of the single-photon e+e− annihilation to hadrons explicitly considered in this work . Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and th e absolute branching fractions in many experiments. Usingthe result presented and the world average values of the electron and hadron branchin g fractions, one obtains the electron partial width and the total width of the ψ(2S ): Γee = 2.282± 0.015± 0.038± 0.021 keV, Γ = 296± 2± 8± 3 keV. These results are consistent with and more than two times mor e precise than any of the previous experiments.

Measurement of ψ(3770) parameters

Abstract We report the final results of a study of the ψ ( 3770 ) meson using a data sample collected with the KEDR detector at the VEPP-4M electron–positron collider. The data analysis takes into account interference between the resonant and nonresonant D D ¯ production, where the latter is related to the nonresonant part of the energy-dependent form factor F D . The vector dominance approach and several empirical parameterizations have been tried for the nonresonant F D N R ( s ) . Our results for the mass and total width of ψ ( 3770 ) are M = 3779.2 − 1.7 + 1.8 − 0.7 + 0.5 − 0.3 + 0.3 MeV , Γ = 24.9 − 4.0 + 4.6 − 0.6 + 0.5 − 0.9 + 0.2 MeV , where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: ( 1 ) Γ e e = 154 − 58 + 79 − 9 + 17 − 25 + 13 eV , ( 2 ) Γ e e = 414 − 80 + 72 − 26 + 24 − 10 + 90 eV . Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non- D D ¯ decays but is disfavored by potential models. It is shown that taking into account the resonance–continuum interference in the near-threshold region affects resonance parameters, thus the results presented cannot be directly compared with the corresponding PDG values obtained ignoring this effect.

Measurement of R uds and R between 3.12 and 3.72 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M e + e − e + e − collider, we have measured the values of R uds R uds and R at seven points of the center-of-mass energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or better than 3.3% 3.3 % at most of energy points with a systematic uncertainty of about 2.1% 2.1 % . At the moment it is the most accurate measurement of R(s) R ( s ) in this energy range.

Measurement of R between 1.84 and 3.05 GeV at the KEDR detector

Abstract 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 % .

Measurement of Γee(J/ψ)⋅B(J/ψ→e+e−) and Γee(J/ψ)⋅B(J/ψ→μ+μ−)

The products of the electron width of the J/ψJ/ψ meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron–positron collider. The results are Γee×Γee/Γ=0.3323±0.0064(stat.)±0.0048(syst.) keV,Γee×Γee/Γ=0.3323±0.0064(stat.)±0.0048(syst.) keV, Γee×Γμμ/Γ=0.3318±0.0052(stat.)±0.0063(syst.) keV.Γee×Γμμ/Γ=0.3318±0.0052(stat.)±0.0063(syst.) keV. Their combinations Γee×(Γee+Γμμ)/Γ=0.6641±0.0082(stat.)±0.0100(syst.) keV,Γee×(Γee+Γμμ)/Γ=0.6641±0.0082(stat.)±0.0100(syst.) keV, Γee/Γμμ=1.002±0.021(stat.)±0.013(syst.)Γee/Γμμ=1.002±0.021(stat.)±0.013(syst.) can be used to improve the accuracy of the leptonic and full widths and test leptonic universality. Assuming eμ universality and using the world average value of the lepton branching fraction, we also determine the leptonic Γll=5.59±0.12 keVΓll=5.59±0.12 keV and total Γ=94.1±2.7 keVΓ=94.1±2.7 keV widths of the J/ψJ/ψ meson.The products of the electron width of the J/\psi meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results are \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-)=(0.3323\pm0.0064\pm0.0048) keV, \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)=(0.3318\pm0.0052\pm0.0063) keV. Their combinations \Gamma_{ee}\times(\Gamma_{ee}+\Gamma_{\mu\mu})/\Gamma=(0.6641\pm0.0082\pm0.0100) keV, \Gamma_{ee}/\Gamma_{\mu\mu}=1.002\pm0.021\pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming e\mu universality and using the world average value of the lepton branching fraction, we also determine the leptonic \Gamma_{ll}=5.59\pm0.12 keV and total \Gamma=94.1\pm2.7 keV widths of the J/\psi meson.

Measurement of D0 and D + meson masses with the KEDR Detector

Abstract The masses of the neutral and charged D mesons have been measured with the KEDR detector at the VEPP-4M electron–positron collider: M D 0 = 1865.30 ± 0.33 ± 0.23 MeV , M D + = 1869.53 ± 0.49 ± 0.20 MeV .

The development of high resolution coordinate detectors for the DEUTERON facility

The DEUTERON internal target facility at the VEPP-3 storage ring at BINP is intended for the experiments on interaction of electrons and positrons with proton and deuteron. These experiments require high resolution tracking detectors which can provide the energy and angles of scattered electron. The prototype detector with a sensitive area of 160 × 40 mm2 was built and proved to be operational. It consists of three cascades of gaseous electron multiplier (GEM), the readout structure and detector electronics. Readout structure has 640 strips which are uniformly distributed in two layers skewed by 30 degrees. Electronics of the detector includes APC128 ASICs, Altera Cyclone III FPGA, 100 MBit ethernet. In the APC128 ASIC each channel has a separate analog pipeline consisting of 32 cells which are cyclically switched by a global clock synchronized to the bunch crossing rate ( ~ 4 MHz). For the needs of DEUTERON facility the expected resolution of less than 100 μm and thickness of ~ 0.15% of radiation length are considered to be quite satisfactory. The latest results obtained at the test beam facility at the VEPP-4M collider show that detector is fully operational with maximum detection efficiency reached 98%.

Threshold aerogel Cherenkov counters of the KEDR detector

Particle identification system based on aerogel threshold Cherenkov counters ASHIPH (Aerogel SHifter PHotomultiplier) was installed in the KEDR detector in 2013. The system consists of 160 counters arranged in two layers and contains 1000 liters of aerogel with refractive index of 1.05 and 160 MCP PMTs with multialkali photocathode. The efficiency of relativistic particles detection was measured. Long-term stability of ASHIPH counters was studied. The main reasons of efficiency degradation are presented.

Extracted electron and gamma beams in BINP

Facility of the extracted beams of electrons and gammas based on the e+e− 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.

Development of high resolution tracking detectors with Gas Electron Multipliers

Cascaded Gas Electron Multipliers (GEM) allow to construct detectors for charge particles tracking with high spatial resolution and rate capability. Such detectors can withstand high background fluxes up to 105 particles/mm2/s and determine track coordinates with precision of 50 – 70 micron. These remarkable features of GEM govern the use of this technology in a number of experiments at the Budker Institute of Nuclear Physics. In this paper the current status and progress in the performance studies and the development of the detectors for the tagging system of the KEDR experiment at the VEPP-4M collider and for the DEUTERON facility at the VEPP-3 storage ring will be covered. The new proposals for the upgrade of tracking and trigger system of the CMD-3 detector, the tracking detectors for the extracted beam from the VEPP-4M storage ring and the tracking detectors for the polarimeter at the VEPP-4M with the use of GEM technology will be discussed.