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To set limits on the ratios of different flavor final states we have treated the observed number of events of each category as independent Poisson variables. In such a case, the exact confidence intervals at a confidence level 1 − α are given by the following formula [30]: 

<img src='content_image/352397.jpg'>

where F ( p ; a, b ) is the cumulative distribution function of a Beta distribution with param- eters a and b , at a value p , and n$_{1}$$_{,}$$_{2}$ are the observed numbers of events. B$_{L}$ and B$_{U}$ are the lower and upper bounds, respectively. The results are shown in Figs. 7 and 8. For the ratio N$_{eµ}$/ ( N$_{ee}$ + N$_{µµ}$ ), the presence of small number of signal events in the µ $^{±}$e∓ final state, due to misclassification, slightly weakens the obtained upper limit. This effect however is very small; to demonstrate this we also consider an “ideal” scenario in which the number of observed events N$_{eµ}$ is set exactly to zero, as would be expected in our model in case of perfect reconstruction and no backgrounds. Those ideal limits are also shown in Fig. 8. For example, for a heavy lepton mass of m$_{χ}$ = 500 GeV and with 30 fb − $^{1}$, the upper bound is 

