Speaker
Vladimir Blinov
(Budker Institute of Nuclear Physics)
Description
An accurate knowledge of the colliding beam energies is essential for the current experiments with the KEDR detector at the VEPP-4M collider. Now the experimental activity is focused on the measurements of $\tau$~lepton mass and parameters of narrow resonances of the $\psi$-family in the c.m.energy range of 3.0--4.0~GeV. Two complementary approaches are used for the beam energy measurements. The Resonant spin Depolarization technique (RD) provides an accuracy about 1--3~keV for the instantaneous beam energy value, but requires a special regime of the collider. Between calibrations the interpolation procedure is used providing the accuracy of 6--10~keV for the $J/\psi,\psi(2s)$ and 15--30~keV for the $\tau$~lepton mass determination experiments.
Another approach allows to calculate beam energy via the maximum energy of backscattering laser photons. The Compton BackScattering (CBS) monitor allows continuous on-line monitoring of the beam energy with accuracy about 120~keV, which is critical during then $\tau$~lepton mass measurement. The statistical error for a one hour period is about 100~keV, the present systematic error is 50~keV.
Summary (Additional text describing your work. Can be pasted here or give an URL to a PDF document):
http://icfa-usa.jlab.org/archive/newsletter/icfa_bd_nl_48.pdf
Author
Vladimir Blinov
(Budker Institute of Nuclear Physics)
