Model-independent search for the Abelian Z' boson and the LEP data

Model-independent search for the Abelian $Z'$ gauge boson virtual state based on the new observable in the processes $e^+ e^- \to l^+ l^-$ is analyzed for the LEP data. The observable is introduced by using following from renormalizability of an underlying theory the correlations between the parameters of the low energy effective Lagrangian and kinematics of the scattering processes. The central values of the observable are in accordance with the $Z'$ existence, although no real signal is found at the $1\sigma$ level. Lower limits at the 95% confidence level on the corresponding contact interaction scale are derived in the range of 15.6 - 18.6 TeV. Comparisons with other fits are done.