m$_{T}$ $^{W}$ [GeV] Number of entries 0 200 400 600 800 1000 0 20 40 60 80 100 120 correct assignment wrong (m  = 600 GeV) correct assignment wrong (m  = 1000 GeV) FIG. 4: Distributions of the W transverse mass with correct (red) and wrong (blue) lepton assign- ments, for heavy lepton masses of 600 (solid) and 1000 (dotted) GeV. with a heavy neutral lepton pair and the same final state (3.2). The transverse mass of the heavy neutral lepton was calculated according to If the Z/h is highly boosted, it can be reconstructed as a single jet. Therefore in the case that there is only a single reconstructed jet in the event with p$_{T}$ > 50 GeV, p$_{j}$$_{2}$ is omitted from (3.5). The distributions of the reconstructed m$_{χ}$ ± and m χ 0 T are shown in Fig. 5, for m$_{χ}$ = 700 GeV. 12 m 2 χ ± = ( p$_{j}$$_{1}$ + p$_{j}$$_{2}$ + p$_{ℓ}$ ) $^{2}$. (3.5) ( m χ 0 T ) 2 = m 2 ℓ $^{+}$ℓ − + 2( E χ 0 T p miss T − p χ 0 T · p miss T ) , (3.4) The invariant mass of the heavy charged lepton was reconstructed from the momenta of the two highest p$_{T}$ jets in the event and the lepton that has opposite charge to that of the W : where p χ 0 T = p ℓ + T + p ℓ − T , with ℓ + and ℓ − the two leptons associated with the χ 0 → W $^{+}$ℓ − → νℓ $^{+}$ℓ − decay, and E χ 0 T = √ m 2 ℓ $^{+}$ℓ − + | p χ 0 T | $^{2}$.