== VLQ Model ==

=== Authors ===

   * Mathieu Buchkremer 
      * Universite catholique de Louvain (CP3)
      * mathieu.buchkremer@uclouvain.be

   * Giacomo Cacciapaglia 
      * Universite de Lyon (CNRS/IN2P3)
      * g.cacciapaglia@ipnl.in2p3.fr

   * Aldo Deandrea 
      * Universite de Lyon (CNRS/IN2P3)
      * deandrea@ipnl.in2p3.fr

   * Luca Panizzi 
      * University of Southampton (School of Physics and Astronomy)
      * l.panizzi@soton.ac.uk
    
=== Description ===
    
This model is an extension of the Standard Model (SM) with new top partners, intended for model-independent searches of vector-like quarks. The corresponding FeynRules implementation is based on a minimal effective Lagrangian description, which provides a direct connection between experimental observables and the new quark couplings. All fields and parameters are defined accordingly to the parameterisation detailed in [1]. The particle content, Feynman rules and parameters of the model are summarized in Parameters.pdf. 
    
=== Model Implementation ===
As a generic framework, the four states $X_{5/3}$, $T_{2/3}$, $B_{-1/3}$ and $Y_{-4/3}$ are introduced as new spin 1/2 class members. Each class defines a specific top partner with a fixed electric charge, without any assumption on the other quantum numbers. The model files are designed to allow for a straightforward extension to additional vector-like fermions, simply by adding the new particles to the corresponding class (F[5], F[6], F[7] and F[8] for $X_{5/3}$, $T_{2/3}$, $B_{-1/3}$ and $Y_{-4/3}$ type quarks, respectively). Particles embedded in larger SU(2) representations may also be introduced under new classes, following the same model-independent prescription.
    
Together with the new fermion fields definitions, the following interactions are added to the SM Lagrangian