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In 2002 experiments with the
universal magnetic detector KEDR at the e+e- collider
VEPP-4M in the Budker institute of nuclear physics in Novosibirsk began.
The detector will operate in wide energy region, accessible for
the VEPP-4M, 2E=2-11 GeV. Especially interest for research
represent psi and upsilon families with rich physics.
KEDR is one of 5 large detectors, operating in this region,
in the world. Unlike other experiments, in the VEPP-4M/KEDR experiment
the precision calibration of energy of beams
by means of the resonant depolarization method (accuracy ~0.001%) and
the method of Compton backscattering (accuracy ~0.003%) is used.
This, in particular, gives possibility to perform measurements of
masses of elementary particles with high precision.
The experiments with the detector started in the energy region of
psi-mesons. Now (in 2008) precision measurements of masses of
the J/psi-meson, psi'-meson, psi(3770)-meson, D-mesons,
tau-lepton were performed.
As a result of the measurements, the masses of J/psi- and psi'-meson
serving the base of the psi-family spectroscopy, were measured with
an accuracy 3-4 times better as compared to the world average.
Parameters of other particles were measured with accuracy, comparable
with the world average. Collection of statistics and data processing
are in progress.
Further plans of experiments with the KEDR detector
include measurement of R in the whole accessible for the VEPP-4M
energy region and transition to high energy, to the area of upsilon-mesons,
where study of two-photon reactions will be performed also.
In two-photon physics we plan
to carry out new measurements of
two-photon widths
of known C-even resonances, to measure with
high precision the total
cross-section of two-photon hadron
production, and to perform a search
for new states.
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