  We consider the problem of correct measurement of a quantum entanglement in
the two-body electron-electron scattering. An expression is derived for a spin
correlation tensor of a pure two-electron state. A geometrical measure of a
quantum entanglement as the distance between two forms of this tensor in
entangled and separable cases is presented. We prove that this measure
satisfies properties of a valid entanglement measure: nonnegativity,
discriminance, normalization, non-growth under local operations and classical
communication. This measure is calculated for a problem of electron-electron
scattering. We prove that it does not depend on the azimuthal rotation angle of
the second electron spin relative to the first electron spin before scattering.
Finally, we specify how to find a spin correlation tensor and the related
measure of a quantum entanglement in an experiment with electron-electron
scattering.
