m$_{χ}$ [GeV] $_{N}$µµ/N ee 500 600 700 800 900 1000 0 0.5 1 1.5 2 2.5 30 fb −1 100 fb −1 300 fb −1 95% Confidence intervals only degraded due to backgrounds from approximately 0.02 to 0.03. FIG. 7: The power of the LHC experiments to constrain the ratio N$_{µ}$ $^{+}$µ − /N$_{e}$ $^{+}$e − (for models where this ratio is unity) as a function of the heavy lepton mass. A value outside the colored area can be rejected at 95% CL for the corresponding integrated luminosity (dark green, light green, yellow for, respectively, 300, 100, 30 fb − $^{1}$). The obtained limits are given for the ratios of observed number of events. Within a real- istic experimental environment one would have to take into account the different detection efficiencies of electrons vs. muons (which are approximately equal in PGS). The difference in energy resolution might also play a role. This effect is expected, however, to be very small, since the resolutions of the reconstructed masses ( m χ 0 T and m$_{χ}$ ± ) are mostly driven by the energy resolution of jets. The ratio of reconstruction efficiencies of electrons vs. muons could be measured to a very high accuracy by comparing e.g. Z → e $^{+}$e − to Z → µ $^{+}$µ − events. With O (10 $^{5}$) such events expected per 1 fb − $^{1}$, the attainable uncertainty of the efficiency ratio is expected to be negligible for our purposes. Thus, while a detailed study of such experimental effects is beyond the scope of this work, we expect the results presented here to be robust. 15