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.
The KEDR Tagging System is designed to enhance the detector ability to study the two-photon processes e super(+)e super(-) arrow right e super(+)e super(-)X. The collider magnetic elements (dipoles ...and lenses) form a focusing magnetic spectrometer for the Scattered Electrons and positrons (for brevity SE). Its energies are measured with 8 coordinate blocks which are placed beside of the vacuum chamber. In the double-tag mode (when both SE are detected) an invariant mass of the system X can be measured with the resolution 3-15 MeV for W sub(inv)(X) = 300 4- 4000 MeV depending on the W and the beam energy. The changes of the beam energy produce some changes in the magnetic structure and the beam orbit. These changes cause systematic shifts of the measured SE energy in TS blocks. The shifts leads to degradation of the W sub(inv)(X) resolution. The complex calibration system was constructed to allow the calibration for all TS blocks with the necessary accuracy.
To high precision measurement of Upsilon -meson masses with KEDR detector on VEPP-4M collider the beam energy calibration is needed. The project of laser polarimeter for beam energy measurement by ...resonance depolarization method is discussed. The polarization measurement is based on up-down asymmetry of Compton backscatterring of circular polarized photons on vertical polarized electrons. Scattered photons are registered by two-coordinate detector based on Gas Electron Multiplier. Expected effect is about 1.6 % with 10sigma a confidence level.
The singly Cabibbo-suppressed decay D+s → K + π + π − π 0 is observed by using a data set corresponding to an integrated luminosity of 6.32 fb − 1 recorded by the BESIII detector at the ...centre-of-mass energies between 4.178 and 4.226 GeV. The first amplitude analysis of D+s → K + π + π − π 0 reveals the sub-structures in this decay and determines the fractions and relative phases of different intermediate processes. The dominant intermediate process is D+s → K *0 ρ + , with a fit fraction of (40 . 5 ± 2 . 8 stat . ± 1 . 5 syst . )%. With the detection efficiency based on our amplitude analysis, the absolute branching fraction for D+s → K + π + π − π 0 is measured to be (9 . 75 ± 0 . 54 stat . ± 0 . 17 syst . ) × 10 − 3 .
Upgrade of beam energy measurement system at BEPC-II 张建勇 蔡啸 莫晓虎 郭迪舟 刘佰奇 M. N. Achasov A. A. Krasnov N.Yu. Muchnoi E. E. Pyata E. V. Mamoshkina F. A. Harris
Chinese physics C,
07/2016, Letnik:
40, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The beam energy measurement system is of great importance for both BEPC-II accelerator and BES-III detector. The system is based on measuring the energies of Compton back-scattered photons. In order ...to meet the requirements of data taking and improve the measurement accuracy, the system has continued to be upgraded, which involves the updating of laser and optics subsystems, replacement of a view-port of the laser to the vacuum insertion subsystem, the use of an electric cooling system for a high purity germanium detector, and improvement of the data acquisition and processing subsystem. The upgrade system guarantees the smooth and efficient measurement of beam energy at BEPC-II and enables accurate offline energy values for further physics analysis at BES-III.
The status of VEPP-4 Blinov, V. E.; Bobrovnikov, V. S.; Zolotarev, K. V. ...
Physics of particles and nuclei letters,
09/2014, Letnik:
11, Številka:
5
Journal Article
Recenzirano
The VEPP-4 accelerator-accumulator complex is designed for carrying out experiments with colliding electron-positron beams with the energy in the range of from 1 to 5 GeV using a VEPP-4M collider ...equipped with the KEDR magnetic detector. Experiments in the field of high-energy physics (HEP) using the complex in its present state have been being carried out since 2002. Science programs other than HEP programs are carried out in the VEPP-4, including experiments with synchrotron-radiation (SR) beams and studies on nuclear physics with an internal gas target, on verification of the CPT invariance, on accelerator physics, etc. The status of the complex, main results, methods used, new approaches, and long-term plans have been described.
The KEDR detector Anashin, V. V.; Aulchenko, V. M.; Baldin, E. M. ...
Physics of particles and nuclei,
07/2013, Letnik:
44, Številka:
4
Journal Article
Recenzirano
The KEDR detector is a universal magnetic detector designed for studying the
c
- and
b
-quarks and two-photon physics, and is employed at the VEPP-4M
e
+
e
−
collider. A specific feature of the ...experiment is the measurement of absolute beam energy using two methods: the resonant depolarization and the faster but less precise Compton backscattering of laser photons. This allowed a large series of measurements to be performed, in which the accuracy of determination of such fundamental parameters of particles as mass and total and leptonic widths was improved.
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