Status of laser polarimeter at VEPP-4M Blinov, V.E.; Bedareva, T.V.; Zakharov, S.A. ...
Journal of instrumentation,
08/2020, Letnik:
15, Številka:
8
Journal Article
Recenzirano
Laser polarimeter facility at VEPP-4M accelerator is designed to calibrate the beam energy by resonance depolarization method in the energy region of the Υ-meson. The laser trigger and laser ...polarization control system has been upgraded. A new water-cooled vacuum mirror is being developed.
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.
The Laser Polarimeter is being developed at VEPP-4M collider for beam energy calibration by Resonant Depolarization technique. The essential part of this facility is a photon-tracking detector ...measuring coordinates of backscattered gammas. The detector is based on triple-GEM cascade with pad readout. Its design and the first results of the measurements with radioactive source are described in the paper.
The beam energy measurement system (BEMS) for the upgraded Beijing electron–positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. ...The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2×10−5. The relative uncertainty of the beam's energy spread is about 6%.
A laser polarimeter at the VEPP-4M storage ring is being developed for the beam energy calibration by the resonant depolarization method in the future high-precision measurements of the Υ meson ...masses with the KEDR detector. The status of the laser polarimeter and first energy measurements at 4.1 GeV with an accuracy of 50 keV is described.
Tau mass measurement at BES-III Achasov, M.N.; Mo, X.H.; Muchnoi, N.Yu ...
EPJ Web of Conferences,
2019, Letnik:
212
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
A scan of the threshold region of the process
e
+
e
−
→ τ
+
τ
−
with integrated luminosity about 140 pb
−1
was performed with the BES-III detector at the BEPC-II collider in order to measure the ...τ-lepton mass. The beam energy was determined by the Compton backscattering method. To verify the measurement accuracy scans of the
J
/ψ and ψ
′
resonances were performed.
The ratio of the electron and muon widths of the J/ psi J/ psi meson has been measured using direct J/ psi J/ psi decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result ...Gamma e+e-(J/ psi )/ Gamma mu + mu -(J/ psi )=1.0022 plus or minus 0.0044 plus or minus 0.0048(0.65%) is in good agreement with the lepton universality. The experience collected during this analysis will be used for J/ psi J/ psi lepton width determination with up to 1% accuracy.
Measurement of parameters Anashin, V V; Aulchenko, V M; Baldin, E M ...
Physics letters. B,
05/2012, Letnik:
711, Številka:
3-4
Journal Article
Recenzirano
We report the final results of a study of the psi ( 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 macr 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 psi ( 3770 ) are M = 3779.2 - 1.7 + 1.8 - 0.7 + 0.5 - 0.3 + 0.3 MeV , Gamma = 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 ) Gamma e e = 154 - 58 + 79 - 9 + 17 - 25 + 13 eV , ( 2 ) Gamma 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 macr 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.
A high-precision determination of the main parameters of the psi ( 2 S ) resonance has been performed with the KEDR detector at the VEPP-4M e + e - collider in three scans of the psi ( 2 S ) - psi ( ...3770 ) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the psi ( 2 S ) we obtained the mass value M = 3686.114 plus or minus 0.007 plus or minus 0.011 - 0.012 + 0.002 MeV and the product of the electron partial width by the branching fraction into hadrons Gamma e e B h = 2.233 plus or minus 0.015 plus or minus 0.037 plus or minus 0.020 keV . The first and second uncertainties are statistical and systematic, respectively. The third uncertainty quoted is an estimate of the model dependence of the result due to assumptions on the interference effects 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 the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the psi ( 2 S ) : Gamma e e = 2.282 plus or minus 0.015 plus or minus 0.038 plus or minus 0.021 keV , Gamma = 296 plus or minus 2 plus or minus 8 plus or minus 3 keV . These results are consistent with and more than two times more precise than any of the previous experiments.
Scenarios for the τ mass measurement at the upgraded Beijing Electron-Positron Collider （BEPC- II ） are studied. A nested minimization procedure is used to optimize the data taking plan. It is found ...that by using five energy points with the total integrated luminosity of 100 pb-1, the τ mass can be determined with a statistical error of 50 keV.
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