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This file show how you can typset a text with Feynman diagrams in equations.

feynman_equations.tex

% Author: Izaak Neutelings (July 2017)
 
\documentclass[10pt,a4paper]{article}
\usepackage[margin=2.4cm]{geometry} % margins
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{feynmp}
 
% macro to compile Feynman graphs without extra scripts
\DeclareGraphicsRule{*}{mps}{*}{}
\makeatletter
\def\endfmffile{
  \fmfcmd{\p@rcent\space the end.^^J end.^^J endinput;}
  \if@fmfio
    \immediate\closeout\@outfmf
  \fi
  %\ifnum\pdfshellescape=\@ne
  \ifnum\pdfshellescape>\z@
    \immediate\write18{mpost \thefmffile}
  \fi}
\makeatother
 
\begin{document}
 
 
 
\section{Typesetting equations with Feynman diagrams}
 
This is an equation of the dominant correction to the Higgs mass squared, containing a Feynman diagram:
\begin{equation}\label{eq:hierarchy_problem}
\begin{fmffile}{higgs_mass_correction}
    \Delta m_H^2
    \,\, = \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=$\text{t}$}{v1,v2,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\ldots
    \,\, = \,\, -\frac{|\lambda_\text{t}|^2}{8\pi}\Lambda^2 + \ldots
\end{fmffile}
\end{equation}
 
% SUSY
One solution to avoid finetuning in Eq.~\eqref{eq:hierarchy_problem} is supersymmetry (SUSY), which assumes each fermion has a scalar superpartner. SUSY will introduce an extra loop diagram: \vspace{5mm}
\begin{equation}\label{eq:hierarchy_problem_SUSY}
  \begin{fmffile}{higgs_mass_correction_SUSY}
    \Delta m_H^2
    \,\, = \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=$\text{t}$}{v1,v2,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmftop{m}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmflabel{$\widetilde{\text{t}}$}{m}
       \fmf{dashes,tension=1}{i,v1}
       \fmf{dashes,tension=1}{v1,o}
       \fmf{dashes,right,tension=0}{v1,m,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\ldots
  \end{fmffile}
\end{equation}
 
% VLQ
Yet another solution are vector-like quarks (VLQs): \vspace{5mm}
\begin{equation}\label{eq:hierarchy_problem_VLQ}
\begin{fmffile}{higgs_mass_correction_VLQ}
    \Delta m_H^2
    \,\, = \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=$\text{t}$}{v1,v2,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=$\text{t}$}{v2,v1}
       \fmf{fermion,left,tension=0.4,label=$\text{T}$}{v1,v2}
    \end{fmfgraph*}}
    \,\, + \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmftop{m}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmflabel{$\text{T}$}{m}
       \fmf{dashes,tension=1}{i,v1}
       \fmf{dashes,tension=1}{v1,o}
       \fmf{fermion,right,tension=0}{v1,m,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\ldots
\end{fmffile}
\end{equation}
 
Notice that in the code, the stop $\widetilde{\text{t}}$ and VLQ top partner T labels were stick out, so an extra \verb|\vspace{5mm}| was needed above the equation.\\
 
Also note that the \verb|align| might not compile. Instead, use the \verb|aligned| environment within the \verb|equation| environment. For example:
\begin{equation}\label{eq:hierarchy_problem}
\begin{aligned}
  \Delta m_H^2 \,\, &=
  \begin{fmffile}{higgs_mass_correction}
    \,\,\parbox{80pt}{
    \begin{fmfgraph*}(80,60)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=$\text{t}$}{v1,v2,v1}
    \end{fmfgraph*}}
    \,\, + \,\,\ldots
  \end{fmffile}\\
   &= \,\, -\frac{|\lambda_\text{t}|^2}{8\pi}\Lambda^2 \,\, + \,\,\ldots
\end{aligned}
\end{equation}
 
 
 
\end{document}