Measurement of R value in the preasymptotic energy region
K.Yu. Todysheva,b aBudker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, prosp. akad. Lavrenteva 11, Novosibirsk, 630090, Russian Federation bNovosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russian Federation
Among the observed variety of natural phenomena reflected in the
experimental results, there are not many physical characteristics,
which allows to see a particular fragment of the mosaic of physical laws
entirely. It is to such a vivid fundamental characteristic
relates the ratio of the inclusive cross section of the electron-positron
annihilation into hadrons to the Born cross section of the muon pair production is referred to as the value of R.
Experiments on measuring the ratio R (s) in the range
energies from 1.84 to 3.72 GeV are considered in this review.