=== Author ===
Richard Ruiz, University of Durham (IPPP) richard.ruiz[at]durham.ac.uk


=== Model Description === 



After electroweak symmetry breaking, the effective Type I Seesaw Lagrangian is given by [#Atre [1]]
{{{ 
#!latex 
$\mathcal{L}_{\rm Type~I} = \mathcal{L}_{\rm SM} + \mathcal{L}_{N} + \mathcal{L}_{N~\text{Int.}} $,
}}}
where { #!latex $\mathcal{L}_{\rm SM}$ } is the Standard Model Lagrangian, the heavy Majorana neutrino's kinetic and mass terms are given by 
{{{ 
#!latex 
$\mathcal{L}_{N} = \frac{1}{2}\overline{N} i\!\not\!\partial N - \frac{1}{2}M_N \overline{N}N$,
}}}
and its interaction terms with the Weak gauge and Higgs bosons in the mass eigenbasis, i.e., after mixing with active neutrinos, by
{{{ 
#!latex 
\begin{eqnarray}
\mathcal{L}_{N~\text{Int.}} &=& -\frac{g}{\sqrt{2}}W_{\mu}^{+}\sum_{\ell=e}^{\tau} \overline{N^{c}}V_{\ell N}^{*}\gamma^{\mu}P_{L}\ell^{-}
\\
& &-\frac{g}{2\cos\theta_W}Z_{\mu}\sum_{\ell=e}^{\tau} \overline{N^{c}}V_{\ell N}^{*}\gamma^{\mu}P_{L}\nu_\ell
\\
& & -\frac{g m_N}{2 M_W} h \sum_{\ell=e}^{\tau} \overline{N^{c}}V_{\ell N}^{*}P_{L}\nu_\ell
+{\rm H.c.}
\end{eqnarray}
}}} 

=== Model Files === 

=== Validation ===

=== References === 
[=#Atre] [1] A. Atre, T. Han, S. Pascoli and B. Zhang, The Search for Heavy Majorana Neutrinos, JHEP '''0905''', 030 (2009)  arXiv:0901.3589 [hep-ph]

[=#point2] [2] D. Alva, T. Han, R. Ruiz, Heavy Majorana neutrinos from {{{#!latex $W\gamma$}}} fusion at hadron colliders, JHEP '''1502''', 072 (2015), arXiv:1411.7305 [hep-ph]