| Paper |
Title |
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| TUPCH074 |
Fast and Precise Beam Energy Monitor Based on the Compton Backscattering at the VEPP-4M Collider
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1181 |
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- N.Yu. Muchnoi, S.A. Nikitin, V.N. Zhilich
BINP SB RAS, Novosibirsk
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Accurate knowledge of the colliding beam energies is essential for the current experiments with the KEDR \cite{KEDR} detector at the VEPP-4M collider. Now the experimental activity is focused on the new precise measurement of the tau-lepton mass by studying the behavior of the tau production cross-section near the reaction threshold. To achieve the desired quality of the experiment, an on-line beam energy monitoring by the Compton backscattering of laser light was performed. This approach is found to be a very good supplement to rare energy calibrations by the resonant depolarization technique, saving the beam time for luminosity runs. The method itself does not require electron beam polarization and additionally allows one to measure the electron beam energy spread. The achieved accuracy of the method in the beam energy range 1.7–1.9 GeV is 60 keV.
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| MOPLS038 |
Beam Energy Calibration in Experiment on Precise Tau Lepton Mass Measurement at VEPP-4M with KEDR Detector
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625 |
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- A. Bogomyagkov, V.E. Blinov, S. Karnaev, V. Kiselev, E.V. Kremyanskaya, E. Levichev, O.I. Meshkov, S.I. Mishnev, I. Morozov, N.Yu. Muchnoi, S.A. Nikitin, I.B. Nikolaev, A.G. Shamov, D.N. Shatilov, E.A. Simonov, A.N. Skrinsky, V.V. Smaluk, Yu.A. Tikhonov, G.M. Tumaikin, V.N. Zhilich
BINP SB RAS, Novosibirsk
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Experiment on mass measurement of tau lepton requires an absolute energy calibration. The resonant depolarization technique is used for most accurate (1 keV) but once at a time energy calibration. The measured energy is used for calibration of the germanium detector for Compton backscattering energy monitoring. The developed Compton backscattering facility allows continuous energy monitoring with accuracy of 50 keV for 10 minutes of data acquisition. The tau lepton threshold is in the vicinity of integer spin resonance, which minimizes polarization lifetime in the presence of vertical orbit distortions. Therefore, spin matching of the VEPP-4M is required. The achieved lifetime is sufficient for absolute energy calibration.
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