A study of the Z production cross-section in pp collisions at root s=7 TeV using tau final states
A measurement of the inclusive Z -> tau tau cross-section in p p collisions at root s = 7 TeV is presented based on a dataset of 1.0 fb(-1) collected by the LHCb detector. Candidates for Z -> tau tau decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c(2), which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be sigma(pp)-> Z ->(tau tau) = 71.4 +/- 3.5 +/- 28 +/- 25 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z -> tau tau to Z -> mu mu is determined to be 0.93 +/- 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements.