v 2 1 9 Se p 20 06 Signals of Z ′ boson in the Bhabha process within the LEP 2 data set

The LEP2 data set on the Bhabha process is analyzed with the aim to detect the signals of the heavy virtual Z ′ gauge bosons. The state interacting with the left-handed standard-model doublets and called the Chiral Z ′ is investigated. This particle was introduced already as the low-energy state allowed by the renormalizability of the model. The contribution of the Chiral Z ′ state to the Bhabha process is described by two parameters: the coupling to electrons and the Z-Z ′ mixing angle. The sign-definite one-parameter observable is proposed to measure the Z ′ coupling to the electron current. The one-parameter fit of the data shows no signals of the particle. The alternative two-parameter fit of the differential cross-sections is also performed. It also shows no Chiral Z ′ signals. The comparisons with other fits are discussed.