Detector KEDR tagger

The KEDR Tagging System is designed to enhance the detector ability to study the two-photon processes e+e−→e+e−X. The collider magnetic elements (dipoles and lenses) form a magnetic spectrometer for the scattered electrons and positrons. Its energies are measured with 8 blocks of the drift tube hodoscope which are placed beside of the vacuum chamber. This allows to determine an invariant mass of the system X with resolution 3–15 Mev for at the beam energies . Recently the TS was upgraded with triple-GEM 2-dimensional detectors and a laser Compton scattering calibration system. The energy resolution for the scattered e± at the level 3⋅10−4 was demonstrated.