Precision predictions for Z′Z′-production at the CERN LHC: QCD matrix elements, parton showers, and joint resummation

We improve the theoretical predictions for the production of extra neutral gauge bosons at hadron colliders by implementing the Z′Z′-bosons in the MC@NLO generator and by computing their differential and total cross sections in joint pTpT and threshold resummation. The two improved predictions are found to be in excellent agreement with each other for mass spectra, pTpT spectra, and total cross sections, while the PYTHIA parton and “power” shower predictions usually employed for experimental analyses show significant shortcomings both in normalization and shape. The theoretical uncertainties from scale and parton density variations and non-perturbative effects are found to be +6/−3%+6/−3%, +/−5%+/−5%, and less than +3/−6%+3/−6%, respectively, and thus under good control. The implementation of our improved predictions in terms of the new MC@NLO generator or resummed K   factors in the analysis chains of the Tevatron and LHC experiments should be straightforward and lead to more precise determinations or limits of the Z′Z′-boson masses and/or couplings.