== 4-fermion EFT with FCNC implementation

== Authors:
* Yoav Afik (yoavafik@campus.technion.ac.il)
* Jonathan Cohen (jcohen@campus.technion.ac.il)
* Eitan Gozani
* Enrique Kajomovitz
* Yoram Rozen

Department of Physics, Technion: Israel Institute of Technology Haifa, Israel


== Description of the model:
This is a Contact Interaction (CI) model. 

The lagrangian of the model is described by: \\
$\mathcal{L}_{eff} = \frac{C_{ij}^{U \mu}}{v^2} (\bar{u}_{L}^{i} \gamma_{\mu} u_{L}^{j}) (\bar{\mu}_{L} \gamma_{\mu} \mu_{L}) + \frac{C_{ij}^{D \mu}}{v^2} (\bar{d}_{L}^{i} \gamma_{\mu} d_{L}^{j}) (\bar{\mu}_{L} \gamma_{\mu} \mu_{L})$

[[Image(source:/Users/yoavafik/Desktop/Lagrangian.png)]]

[[Image(/Users/yoavafik/Desktop/matrix.png)]]
/Users/yoavafik/Desktop/matrix.png


<math>
\begin{pmatrix}
x & y \\
z & v
\end{pmatrix}
<\math>

$C_{ij}^{U \mu} = 
\begin{pmatrix} C_{u \mu} & 0 & 0 \\ 0 & C_{c \mu} & 0 \\ 0 & 0 & C_{t \mu} \end{pmatrix} 
,
C_{ij}^{D \mu} = 
\begin{pmatrix} C_{d \mu} & 0 & 0 \\ 0 & C_{s \mu} & C_{b s \mu}^{*} \\ 0 & C_{b s \mu} & C_{t \mu} \end{pmatrix} $

See more details in:
https://link.springer.com/article/10.1007/JHEP08(2018)056



== Sample commands for MadGraph5_aMC@NLO:
{{{
define p = g u c d s b u~ c~ d~ s~ b~ 
define j = g u c d s b u~ c~ d~ s~ b~ 
generate p p > mu+ mu- 
add process p p > mu+ mu- j 
add process p p > mu+ mu- j j 
}}}