We are able to test the diagonality of the couplings in two independent ways, which are described in Section III E. First, the comparison of the number of e $^{+}$e − events to the number of µ $^{+}$µ − events, where the MLFV prediction, for the case that both types of events are observed, is one. (The other possibility, in case of hierarchical spectrum, is that there are only e $^{+}$e − events.) As can be seen from Fig. 7, with 300 fb − 1 and m$_{χ}$ ∼ 500 GeV, this prediction can be tested with an accuracy of order ten percent. With 30 fb − 1 and m$_{χ}$ ∼ TeV, this prediction can be tested to within a factor of 2.5. Second, we can search for eµ events which, according to MLFV, should not be present. As can be seen from Fig. 8, with 300 fb − 1 and m$_{χ}$ ∼ 500 GeV, the ratio between the flavor non-diagonal and flavor-diagonal events can be constrained to lie below the percent level. With 30 fb − 1 and m$_{χ}$ ∼ TeV, the bound is of order 0.6. Low energy searches for flavor changing neutral current decays, such as µ → eγ , put strong constraints on the product of the mass splitting and the mixing angle between the heavy leptons. Regardless of the strength of such low energy constraints, ATLAS/CMS can provide flavor information that is not available from low energy data. In particular, the eµ -test will constrain the mixing angle in the heavy sector for any finite mass splitting. When ATLAS and CMS experiments collect enough data, they will also be able to un- derstand in more detail their capabilities in identifying tau-leptons. It will become possible then to test also all tau-related predictions of Eq. (3.6). While the experimental accuracy of these measurements is expected to be poorer than the tests of Eq. (3.7), it may well be that violations of MLFV predictions are larger when tau-leptons are involved. The analysis proposed in this paper will become much easier if, in addition to the charged heavy leptons, there exists a Z $^{′}$-boson that is light enough to be produced at the LHC and heavy enough to decay into a χ ¯ pair. Indeed, such a scenario, with stable heavy leptons, was described in Ref. [31] as a scenario that can be probed by a low energy and low luminosity initial LHC data set, and which is not ruled out by the Tevatron and other measurements. In such a case, we expect an O (16 π $^{2}$) enhancement in the number of signal events. It would mean that some informative (though rough) flavor measurements will be possible with as little as few hundreds of pb − 1 of integrated luminosity. 17