3 with 5 fb − $^{1}$, use madgraph [23] to model the kinemat- ics of the events, pythia [24] for showering and a version of pgs [25] tuned to describe the performance of the CD- FII detector. At the LHC, the diboson contribution includes an ad- ditional process, qq → W $^{±}$W $^{±}$q$^{′}$q$^{′}$, which directly pro- duces the ℓ $^{±}$ℓ$^{±}$jj signature. For the LHC, we calculate the size and kinematics of each contribution using mad- graph , use pythia for showering and a version of pgs tuned to describe the performance of the ATLAS detec- tor. Figure 3 shows the reconstructed mass shape for N pair production and for the backgrounds in the µ $^{±}$µ$^{±}$jj case. struct frequentist intervals. If the N does not exist and no excess is seen, the median expected upper limits on the cross-section are given in Table I and Fig. 4. In 5 fb − $^{1}$, with BR( N → µW ) = 100%, a single Tevatron (LHC) experiment could expect to set a 95% lower limit of m$_{N}$ > 175 (300) GeV. The limits as a function of BR( N → τW ) are given in Fig. 5. If the N does exist, a 3 σ excess would be observed in the regions shown in Fig. 5. We perform a binned likelihood fit in the reconstructed N mass, and use the unified ordering scheme [26] to con- The s -channel pair production of heavy Majorana neu- trinos via a Z boson ( Z → NN → WℓWℓ ) is a powerful discovery mode at hadron colliders. With 5 fb − 1 of data, the Tevatron can significantly extend the limits on such neutrinos to 175 GeV/ c $^{2}$, and a 3 σ evidence is possible if Expected Limits and Discovery Potential CONCLUSIONS FIG. 5: Median expected 95% C.L experimental exclusion (top) or 3 σ evidence (bottom) in 5 fb − 1 of Tevatron (left) LHC data (right) as a function of BR( N → W τ ). Two decay cases are shown: µ $^{±}$µ± (black) or ℓ $^{±}$ℓ± (red), as defined in the text. FIG. 3: Expected reconstructed neutrino mass for N produc- tion with m N = 150 GeV/ c $^{2}$, and backgrounds to the µ $^{±}$µ$^{±}$jj signature in 5 fb − 1 of Tevatron data (top) or 10 TeV LHC data (bottom). FIG. 4: Theoretical cross-section for N production and de- cay to ℓ $^{±}$W ℓ$^{±}$W and median expected 95% C.L experimental cross-section upper limits in 5 fb − 1 of Tevatron data (left) or LHC data (right), assuming BR( N → µW ) = 100%. ] 2  Mass [GeV/c 4 100 150 200 Cross-section [fb] -1 10 1 10 ] 2  Mass [GeV/c 4 100 200 300 400 Cross-section [fb] -1 10 1 10 2 10 ] 2 Neutrino Mass [GeV/c 80 100 120 140 160 180 200 0.2 0.4 0.6 0.8 1 1.2 1.4 NN Z Diboson Fakes ] 2 Neutrino Mass [GeV/c 100 150 200 250 300 350 400 450 500 0 5 10 15 20 25 NN Z diboson fakes ] 2 Neutrino Mass [GeV/c 100 150  )  W 1 BR( 0 0.2 0.4 0.6 0.8 1 ] 2 Neutrino Mass [GeV/c 200 250 300  )  W 1 BR( 0 0.2 0.4 0.6 0.8 1 ] 2 Neutrino Mass [GeV/c 100 120 140  )  W 1 BR( 0 0.2 0.4 0.6 0.8 1 ] 2 Neutrino Mass [GeV/c 100 150 200  )  W 1 BR( 0 0.2 0.4 0.6 0.8 1