Process W/Z Decay σ × BR [fb] Selection [fb] Z veto [fb] Generated events t ¯ tZ Z → ℓ $^{+}$ℓ − 155.7 2.19 0.052 32.7K t ¯ tW 3 W → 3( ℓν ) 13.95 0.174 0.139 23.7K ZZ 2 Z → 2( ℓ $^{+}$ℓ $^{−}$) 71.6 0.632 0.004 10K W Z Z → ℓ $^{+}$ℓ $^{−}$, W → ℓν 157 0.471 < 0 . 016 10K t ¯ t 2 W → 2( ℓν ) 33329 0.054 0.018 1.8M b ¯ bZ Z → ℓ $^{+}$ℓ − 60000 0.027 < 0 . 027 2.3M Signal 19.0 12.8 12.0 25K Reconstruction of the heavy lepton mass requires the identification of the SM lepton originating from the W decay. One possibility is immediately ruled out, since this lepton can only be one of the two leptons which have the same sign. We have calculated the transverse mass of the W for both of those leptons: The distributions of m W T are shown in Fig. 4, for the correct and for the wrong lepton assignments. The combination that yields the lower value was designated as the W decay product. The correct lepton configuration was selected with this procedure at about 93% of the events. The two remaining opposite sign leptons, assumed to be produced directly by the heavy lepton-pair decays, were then assigned to the charged and neutral lepton decays according to their charges. Note that the above reconstruction procedure equally applies to events 11 ( m W T ) 2 = 2 p ℓ $_{T}$p miss T (1 − cos φ$_{ℓ,}$$_{miss}$ ) , (3.3) D. Reconstruction TABLE II: Number of events corresponding to integrated luminosity of 1 fb − $^{1}$: total (first column); passing the selection criteria before imposing the Z veto (second column); passing all cuts (third column). The last column reports the number of events that we generated for our simulation. The signal sample corresponds to three heavy lepton generations with m$_{χ}$ = 500 GeV. It includes all production and decay modes ( i.e. χ $^{0}$¯ χ $^{0}$, χ$^{+}$χ $^{−}$, χ$^{±}$χ $^{0}$), and the branching ratio refers to a three lepton final state. We use m$_{h}$ = 120 GeV.