Extraction of Coupling Information from Z

An analysis by the ATLAS Collaboration has recently shown, contrary to popular belief, that a combination of strategic cuts, excellent mass resolution, and detailed knowledge of the QCD backgrounds from direct measurements can be used to extract a signal in the Z ′ → jj channel in excess of 6σ for certain classes of extended electroweak models. We explore the possibility that the data extracted from Z dijet peak will have sufficient statistical power as to supply information on the couplings of the Z ′ provided it is used in conjunction with complimentary results from the Z ′ → ll ‘discovery’ channel. We show, for a 1 TeV Z ′ produced at the SSC, that this technique can provide a powerful new tool with which to identify the origin of Z ’s. ∗Research supported by the U.S. Department of Energy, Division of High Energy Physics, Contract W-31-109-ENG-38. The observation of a new neutral gauge boson, Z , at the SSC and/or LHC would be an extremely clear signature for the existence of new physics beyond the Standard Model(SM). Many analyses have shown[1] that such particles are copiously produced at these hadron supercolliders and would be easily detected via their leptonic decay up to masses of order several TeV for most extended electroweak model(EEM) scenarios. Of course once the Z ′ is detected it would be mandatory to determine its various couplings in order to determine, if possible, from which EEM it arose. Quite generally, this has proven to be a more difficult task than one might at first suspect and has lead to a number of possible approaches advocated in the literature during the last three years[2]. These various techniques have included the use of rare decay modes, initially polarized proton beams to produce new asymmetries, associated production of the Z ′ together with other gauge particles, and determining the polarization of final state τ s. All of these analyses have neglected the possibility that hadronic Z ′ decays could be used to obtain coupling information since it is commonly believed[3] that the conventional backgrounds(B) from QCD are so large as to render this mode unobservable. Recently, Henriques and Poggioli(HP) of the ATLAS Collaboration[4] have shown that a combination of strategic cuts, good dijet mass resolution, and detailed determination of the QCD background in the dijet invariant mass neighborhood near the Z ′ can be used to extract a signal(S) in excess of 6σ at the LHC for a Z ′ with a mass of 2 TeV with SM-like couplings. If a determination of the Z ′ → jj production cross section, σjj, can be combined with the corresponding lepton-pair cross section, σl, (which is the Z ′ discovery channel), new information on the Z ’s couplings would be obtained. The purpose of this paper is to analyze this approach for a 1 TeV Z ′ at the SSC, within the context of several EEM. (We choose this mass value in order to make a comparison with the analyses in[2].) For this rather low Z ′ mass, we find there is sufficient statistics available to extract coupling information for at least some of these EEM’s assuming an integrated luminosity of L = 10fb, corresponding