Estimates of Z'couplings within data on the A_{FB} for Drell-Yan process at the LHC at s^(1/2) = 7 TeV and 8 TeV

Abstract

Model-independent search for the Abelian Z' gauge boson in the Drell-Yan process at the LHC at s^{1/2}= 7 TeV and 8 TeV is fulfilled. Estimations of the Z' axial-vector coupling a_f^2 to the standard model fermions, the couplings of the axial-vector to lepton vector currents a_f v_l and the couplings of the axial-vector to quark vector currents a_f v_q are derived within data on the forward-backward asymmetry presented by the CMS Collaboration. The analysis takes into consideration the behaviour of the differential cross-section which exhibits itself if the derived already special relations between the couplings proper to the renormalizable theories are accounted for. In particular, they hold in all the models of Abelian Z' usually considered in the model-dependent analysis of the LHC data. The coupling values are estimated at ~ 92 % CL by means of the maximum likelihood function. They weakly depend on the Z' mass in the investigated interval 1.2 TeV < m_Z' < 5 TeV. Taking into account the dependence of Z-Z' mixing angle theta_0 on m_Z' and the LEP constraints |theta_0|~ 10^{-3}-10^{-4}, the optimistic limits on m_{Z'} are established as 3 < m_Z' < 7-8 TeV. Comparison with the results of other authors is given.