Signals of the Abelian Z′ boson within the analysis of the LEP2 data

Abstract

The preliminary LEP data on the e + e − → l + l − scattering are analysed to establish a model-independent search for the signals of virtual states of the Abelian Z ′ boson. The recently introduced observables give a possibility to pick up uniquely the Abelian Z ′ signals in these processes. The mean values of the observables are in accordance with the Z ′ existence. However, the accuracy of the experimental data is deficient to detect the signal at more than the 1σ confidence level. The results of other model-independent fits and further prospects are discussed.

Hint of aZ′boson from the CERN LEP II data

“…Our analysis of the leptonic processes based on the same data set and the same SM values of cross-sections showed that the existence of Z ′ boson with the mass of order 1-1.2 TeV is not excluded at the 1-2σ CL. We observed this in one-parameter fits [6,7] and in the many-parameter fits in the present paper. The estimated Z ′ parameters derived in different methods are in good agreement with each other.…”

“…As it will be shown, the uncertainty of the many-parametric fit can be comparable with the uncertainty of the previous one-parametric fits in Refs. [6,7]. In this approach the combined data fit for all lepton processes is also possible.…”

“…Searching for this particle in either model-dependent or modelindependent approaches is widely discussed in the literature [4]. In the papers of the present authors [5,6,7] the new method and the observables for the modelindependent search for the Z ′ -boson were proposed and applied to analyze the LEP2 experiment data. In contrast to other model-independent searches, our approach gives a possibility to pick out uniquely this virtual state and determine its characteristics.…”

Model-independent search for the AbelianZ′boson in the Bhabha process

“…[2,4] we showed for the processes e e ÿ ! ÿ ; ÿ , that the many-parametric differential cross section can be integrated over a special range of the scattering angles in order to select only one of the unknown parameters.…”

“…It is interesting to note that the mean values of v 2 are a little larger than those obtained for a 2 for e e ÿ ! ÿ ; ÿ processes [4]. The second fit (''fit 2'') estimates the observable (12) related to the value of a 2 .…”