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The plan of this paper goes as follows. In Section II we present our theoretical framework. In Section III we describe the LHC phenomenology. In Section IV we analyze the lessons concerning minimal flavor violation that can be drawn from the ATLAS/CMS measurements. 

## II. THE THEORETICAL FRAMEWORK 

The SM leptons include the lepton SU (2)-doublets L$_{L}$ and the charged lepton SU (2)- singlets E$_{R}$ . We assume that, in addition to the SM leptons, there exist vector-like leptons, χ$_{L}$ and χ$_{R}$ , which are SU (2)-doublets and carry hypercharge − 1 / 2 (so that the electric charges of the two members in each doublet are 0 and − 1). The most general Yukawa and mass terms of the leptonic sector in this extended framework are the following: 

<img src='content_image/347209.jpg'>

where v = 〈 φ 〉 , and m$_{2}$, M$_{1}$, M$_{2}$ have dimension of mass. The first two terms are Yukawa couplings and the last two bare mass terms. We introduce the ratio m$_{2}$/v into the second term for later convenience. We assume that the electroweak symmetry breaking parameters v and m$_{2}$ are smaller than the electroweak symmetry conserving ones, M$_{1}$ and M$_{2}$ . 

## A. The models 

To implement the MLFV principle, we need to assign the various fields to representations of the lepton flavor symmetry 

By definition, the SM lepton fields are triplets of G$_{LF}$ : 

<img src='content_image/347205.jpg'>

<img src='content_image/347206.jpg'>

and the SM charged lepton Yukawa matrix acts as a spurion which breaks G$_{LF}$ : 

<img src='content_image/347207.jpg'>

We are free to assign the new fields, χ$_{L,R}$ to whichever G$_{LF}$ representation that we wish. The assignment determines the spectrum and the couplings of these fields. We are interested, 

