Hint for axial-vector contact interactions in the data one+e−→e+e−(γ)at center-of-mass energies 192–208 GeV

Abstract

For the first time the experiments ALEPH, DELPHI, L3 and OPAL have presented preliminary results for fermion-pair production in ${e}^{+}{e}^{\ensuremath{-}}$ collisions on the full data set above the Z pole. A combined analysis of the Bhabha scattering measurements is performed to search for effects of contact interactions. In the case of two axial-vector $(\mathrm{AA})$ currents the best fit to the data is 2.6 standard deviations away from the standard model expectation, corresponding to an energy scale $\ensuremath{\Lambda}{=10.3}_{\ensuremath{-}1.6}^{+2.8} \mathrm{TeV}$ for contact interactions. For other models no statistically significant deviations are observed, and the data are used to set lower limits at 95% confidence level on the contact interaction scales ranging from 8.2 to 21.3 TeV, depending on the helicity structure.