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<img src='content_image/353023.jpg'>

## E. Obtaining flavor constraints 

We focus here on model LL, which has three quasi-degenerate heavy leptons, each de- caying to one of the light lepton flavors, e, µ, τ . Events are classified by the flavor of the two leptons associated with the heavy pair decay. We are interested in N$_{ij}$ , the observed numbers of events in each flavor composition ℓ ± i ℓ ∓ j . The MLFV prediction is that 

Our analysis allows us to test two of these predictions, namely 

<img src='content_image/353030.jpg'>

<img src='content_image/353029.jpg'>

For the flavored cross section ratio estimates, we considered events within a window of 150 GeV around the mass peak of both m$_{χ}$ ± and m χ 0 T . As is evident in Fig. 5, standard model background in this region is negligible. In Fig. 6, the reconstructed transverse mass m χ 0 T is shown separately for the three different flavor compositions, e $^{+}$e $^{−}$, µ $^{+}$µ − and e $^{±}$µ$^{∓}$. Ideally, there should be no events in the eµ final state. In practice, however, a small number of the signal events are reconstructed as such, mostly due to misclassification of leptons in the event. Another possible source of contamination are τ pairs, decaying to e and µ , however this contribution was found to be negligible. 

