ttbar production in pp

by Posted on

This posts shows code examples of Feynman diagrams of ttbar production in proton-proton collisions, like those at the Large Hadron Collider (LHC). For a nice overview from the experimental point of view, have a look at this review article by the CMS collaboration, submitted to Physics Reports.

Click on a diagram to jump to the code & download links below:
ttbar-001.png ttbar-002.png ttbar-003.png ttbar-004.png ttbar-005.png ttbar-006.png ttbar-007.png ttbar-008.png ttbar-009.png

Top-quark pair production

Quark-antiquark annihilation:

\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-6,15)(-3,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{fermion}{i1,v1,i2}
    \fmf{fermion}{o2,v2,o1}
    \fmf{gluon,label=$g$,label.side=right,label.dist=10}{v2,v1} % s-channel
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmflabel{t}{o1}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Gluon fusion (s-channel):
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-5,15)(-3,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmfshift{2 left}{i1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{v1,i2}
    \fmf{gluon,label.side=left,label=$g$}{v1,v2} % s-channel
    \fmf{fermion}{o2,v2,o1}
    % labels
    %\fmflabel{$g$}{i1}
    %\fmflabel{$g$}{i2}
    \fmfv{l.d=4,l=$g$}{i1} % more control
    \fmfv{l.d=6,l=$g$}{i2} % more control
    \fmflabel{t}{o1}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
    %\fmflabel{$i\sqrt{\alpha}$}{v1}
    %\fmflabel{$i\sqrt{\alpha}$}{v2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Gluon fusion (t-channel):
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-5,15)(-2,15){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{fermion,t=0.8,l.s=left,label=t}{v2,v1} % t-channel
    \fmf{gluon}{i2,v2}
    \fmf{fermion}{v1,o1}
    \fmf{fermion}{o2,v2}
    % labels
    \fmflabel{$g$}{i2}
    \fmflabel{$g$}{i1}
    \fmfv{l.d=7,l.a=22,l.s=left,l=t}{o1}
    \fmfv{l.d=7,l.a=-20,l=$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Gluon fusion (u-channel):
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-5,15)(-2,15){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{i2,v2}
    \fmf{fermion,t=0.8,l.s=right,label=t}{v1,v2} % t-channel
    \fmf{phantom}{v1,o1,o2,v2} % for balance
    \fmffreeze
    \fmf{fermion}{o2,v1}
    \fmf{fermion,rubout}{v2,o1}
    % labels
    \fmflabel{$g$}{i2}
    \fmflabel{$g$}{i1}
    \fmfv{l.d=5,l.a=25,l.s=left,l=t}{o1}
    \fmfv{l.d=5,l.a=-25,l=$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Without initial-/final-state radiation

Initial-state radiation:

\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-6,18)(-5,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,70) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmftop{t}
    \fmfshift{5 up}{t}
    % skeleton
    \fmf{phantom}{i1,v1,i2}
    \fmf{phantom}{v1,v2}
    \fmf{phantom}{o1,v2,o2}
    \fmffreeze
    % main
    \fmf{fermion}{i1,g}
    \fmf{plain,tension=2.8}{g,v1}
    \fmf{fermion}{v1,i2}
    \fmf{gluon,tension=0}{t,g}
    \fmf{gluon}{v1,v2}
    \fmf{fermion}{o2,v2,o1}
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmfv{l.d=5,l.a=25,l=$g$}{t}
    \fmflabel{$\mathrm{t}$}{o1}
    \fmflabel{$\bar{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex. 

\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-6,18)(-5,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,75) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmftop{t}
    \fmfshift{4 left}{i1}
    \fmfshift{2 left}{i2}
    \fmfshift{5 up}{t}
    % skeleton
    \fmf{phantom}{i1,v1,i2}
    \fmf{phantom}{o1,v2,o2}
    \fmf{phantom,tension=1.2}{v1,v2}
    \fmffreeze
    % main
    \fmf{gluon,tension=0.8}{g,i1}
    \fmf{fermion}{v1,g}
    \fmf{fermion}{i2,v1}
    \fmf{fermion,tension=0}{g,t}
    \fmf{gluon}{v1,v2}
    \fmf{fermion}{o2,v2,o1}
    % labels
    %\fmflabel{$g$}{i1}
    %\fmflabel{$g$}{i2}
    \fmfv{l.d=4,l=$g$}{i1}
    \fmfv{l.d=6,l=$q$}{i2}
    \fmfv{l.d=5,l.a=25,l=$q$}{t}
    \fmflabel{$\bar{\mathrm{t}}$}{o2}
    \fmflabel{$\mathrm{t}$}{o1}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Final-state radiation:
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-8,15)(15,18){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,75) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o,o1}
    \fmfshift{2 up}{o}
    \fmfshift{6 right}{o}
    % main
    \fmf{fermion}{i1,v1,i2}
    \fmf{gluon,label=$g$,label.side=right,label.dist=10}{v2,v1}
    \fmf{phantom}{o2,v2,o1}
    \fmffreeze
    \fmf{fermion}{o2,v2,v,o1}
    \fmf{gluon,t=0}{v,o}
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
    \fmflabel{t}{o1}
    \fmflabel{$g$}{o}
    %\fmfv{decor.shape=circle,decor.filled=full,decor.size=3.5,f=(.7,,.1,,.1)}{v}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

With top quark decay

Semileptonic final state:

\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(4,14)(35,17){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(160,150) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    \fmfset{arrow_len}{3.6mm}
    % external vertices
    \fmfstraight
    \fmfleft{d,i2,i1,d} % add dummies 'd' for spacing
    \fmfright{o6,o5,o4,o3,o2,o1}
    \fmfshift{2 up}{i1}
    \fmfshift{2 down}{i2}
    %\fmfshift{8 left}{o1,o6} % shift b quarks left
    % qq -> g
    \fmf{fermion,t=1.4}{i2,vg,i1}
    \fmf{gluon,t=1.4}{vtt,vg} % gluon s-channel
    % ttbar
    \fmf{fermion,l.s=left,label={$\mathrm{t}$}}{vtt,v1}
    \fmf{fermion,l.s=left,label={$\overline{\mathrm{t}}$}}{v2,vtt}
    % bbbar
    \fmf{fermion,t=0.6}{v1,o1}
    \fmf{fermion,t=0.6}{o6,v2}
    \fmffreeze
    % W -> qq / lnu
    \fmf{boson,t=1.2,label=W$^+$,l.d=5,l.s=left}{v2,w2} % W boson
    \fmf{boson,t=1.2,label=W$^-$,l.d=5,l.s=right}{v1,w1} % W boson
    \fmf{fermion,t=1}{o3,w1,o2} % W decay
    \fmf{fermion,t=1}{o5,w2,o4} % W decay
    \fmf{phantom,t=0.05}{w1,w2} % pull decay vertices together
    % labels
    \fmfv{l.a=155,l.d=4,l=$q$}{i1}
    \fmfv{l.a=-155,l.d=5,l=$\overline{q}$}{i2}
    \fmfv{l.a=25,l.d=5,l=b}{o1}
    \fmfv{l.a=-25,l.d=5,l=$\overline{\mathrm{b}}$}{o6}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$\ell^-$} / $\overline{q}'$}{o2}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{\nu}_\ell$} / $q$}{o3}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$q'$} / $\ell^+$}{o4}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{q}'$} / $\nu_\ell$}{o5}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex. 

\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(4,14)(35,17){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(160,150) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    \fmfset{arrow_len}{3.6mm}
    % external vertices
    \fmfleft{d,i2,i1,d} % add dummies 'd' for spacing
    \fmfright{o6,o5,o4,o3,o2,o1}
    \fmfshift{2 up}{i1}
    \fmfshift{2 down}{i2}
    \fmfshift{4 left}{o1,o6} % shift b quarks left
    % qq -> g
    \fmf{fermion,t=1.1}{i2,vg,i1}
    \fmf{gluon,t=1.1}{vtt,vg} % gluon s-channel
    % ttbar
    \fmf{fermion,l.s=left,label={$\mathrm{t}$}}{vtt,v1}
    \fmf{fermion,l.s=left,label={$\overline{\mathrm{t}}$}}{v2,vtt}
    % bbbar
    \fmf{fermion,t=0.5}{v1,o1}
    \fmf{fermion,t=0.5}{o6,v2}
    \fmffreeze
    % W -> qq / lnu
    \fmf{boson,t=1.1,label=W$^+$,l.d=5,l.s=left}{v2,w2} % W boson
    \fmf{boson,t=1.1,label=W$^-$,l.d=5,l.s=right}{v1,w1} % W boson
    \fmf{fermion,t=1}{o3,w1,o2} % W decay
    \fmf{fermion,t=1}{o5,w2,o4} % W decay
    \fmf{phantom,t=0.2}{w1,w2} % pull decay vertices together
    %\fmf{phantom,t=0.05}{w1,o2,o5,w2} % pull decay vertices to the right
    % labels
    \fmfv{l.a=155,l.d=4,l=$q$}{i1}
    \fmfv{l.a=-155,l.d=5,l=$\overline{q}$}{i2}
    \fmfv{l.a=25,l.d=5,l=b}{o1}
    \fmfv{l.a=-25,l.d=5,l=$\overline{\mathrm{b}}$}{o6}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$\ell^-$} / $\overline{q}'$}{o2}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{\nu}_\ell$} / $q$}{o3}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$q'$} / $\ell^+$}{o4}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{q}'$} / $\nu_\ell$}{o5}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}
Download as .png, .pdf, or .tex.

Full code

The LaTeX code below collects all the diagrams above into one big file that produces a multipage PDF. Please find download links below, or edit and compile here if you like:

% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (February 2023)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape ttbar.tex
\documentclass[11pt,border=-2pt,multi=page,crop]{standalone}
\usepackage{amsmath}
\usepackage{feynmp-auto}

% DEFINE fmfpicture ENVIRONMENT
\usepackage{environ} % for \NewEnviron
\NewEnviron{fmfpicture}[3]{%
  \begin{page} % to create standalone page
  \fmfframe(#1)(#2){ % padding (LT)(RB)
  \begin{fmffile}{feynmp-#3} % auxiliary files (use unique name!)
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    \BODY % main code
  \end{fmffile}
  }
  \end{page}
}

\begin{document}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% TTBAR PRODUCTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% TTBAR PRODUCTION - Quark-antiquark annihilation
\begin{fmfpicture}{-6,15}{-3,16}{qq-ttbar-schan} % padding (LTRB)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{fermion}{i1,v1,i2}
    \fmf{fermion}{o2,v2,o1}
    \fmf{gluon,label=$g$,label.side=right,label.dist=10}{v2,v1} % s-channel
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmflabel{t}{o1}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION - Gluon-gluon fusion (s-channel)
\begin{fmfpicture}{-5,15}{-3,16}{gg-ttbar-schan} % padding (LTRB)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmfshift{2 left}{i1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{v1,i2}
    \fmf{gluon,label.side=left,label=$g$}{v1,v2} % s-channel
    \fmf{fermion}{o2,v2,o1}
    % labels
    %\fmflabel{$g$}{i1}
    %\fmflabel{$g$}{i2}
    \fmfv{l.d=4,l=$g$}{i1} % more control
    \fmfv{l.d=6,l=$g$}{i2} % more control
    \fmflabel{t}{o1}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
    %\fmflabel{$i\sqrt{\alpha}$}{v1}
    %\fmflabel{$i\sqrt{\alpha}$}{v2}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION - Gluon-gluon fusion (t-channel)
\begin{fmfpicture}{-5,15}{-2,15}{gg-ttbar-tchan} % padding (LTRB)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{fermion,t=0.8,l.s=left,label=t}{v2,v1} % t-channel
    \fmf{gluon}{i2,v2}
    \fmf{fermion}{v1,o1}
    \fmf{fermion}{o2,v2}
    % labels
    \fmflabel{$g$}{i2}
    \fmflabel{$g$}{i1}
    \fmfv{l.d=7,l.a=22,l.s=left,l=t}{o1}
    \fmfv{l.d=7,l.a=-20,l=$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION - Gluon-gluon fusion (u-channel)
\begin{fmfpicture}{-5,15}{-2,15}{gg-ttbar-uchan} % padding (LTRB)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{i2,v2}
    \fmf{fermion,t=0.8,l.s=right,label=t}{v1,v2} % t-channel
    \fmf{phantom}{v1,o1,o2,v2} % for balance
    \fmffreeze
    \fmf{fermion}{o2,v1}
    \fmf{fermion,rubout}{v2,o1}
    % labels
    \fmflabel{$g$}{i2}
    \fmflabel{$g$}{i1}
    \fmfv{l.d=5,l.a=25,l.s=left,l=t}{o1}
    \fmfv{l.d=5,l.a=-25,l=$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
\end{fmfpicture}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% TTBAR PRODUCTION + RADIAITON %%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% TTBAR PRODUCTION - Quark-antiquark annihilation + ISR
\begin{fmfpicture}{-6,18}{-5,16}{qq-ttbar-isr} % padding (LTRB)
  \begin{fmfgraph*}(120,70) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmftop{t}
    \fmfshift{5 up}{t}
    % skeleton
    \fmf{phantom}{i1,v1,i2}
    \fmf{phantom}{v1,v2}
    \fmf{phantom}{o1,v2,o2}
    \fmffreeze
    % main
    \fmf{fermion}{i1,g}
    \fmf{plain,tension=2.8}{g,v1}
    \fmf{fermion}{v1,i2}
    \fmf{gluon,tension=0}{t,g}
    \fmf{gluon}{v1,v2}
    \fmf{fermion}{o2,v2,o1}
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmfv{l.d=5,l.a=25,l=$g$}{t}
    \fmflabel{$\mathrm{t}$}{o1}
    \fmflabel{$\bar{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION - Quark-gluon fusion + radiation
\begin{fmfpicture}{-6,18}{-5,16}{gq-ttbar-isr} % padding (LTRB)
  \begin{fmfgraph*}(120,75) % dimensions (WH)
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmftop{t}
    \fmfshift{4 left}{i1}
    \fmfshift{2 left}{i2}
    \fmfshift{5 up}{t}
    % skeleton
    \fmf{phantom}{i1,v1,i2}
    \fmf{phantom}{o1,v2,o2}
    \fmf{phantom,tension=1.2}{v1,v2}
    \fmffreeze
    % main
    \fmf{gluon,tension=0.8}{g,i1}
    \fmf{fermion}{v1,g}
    \fmf{fermion}{i2,v1}
    \fmf{fermion,tension=0}{g,t}
    \fmf{gluon}{v1,v2}
    \fmf{fermion}{o2,v2,o1}
    % labels
    %\fmflabel{$g$}{i1}
    %\fmflabel{$g$}{i2}
    \fmfv{l.d=4,l=$g$}{i1}
    \fmfv{l.d=6,l=$q$}{i2}
    \fmfv{l.d=5,l.a=25,l=$q$}{t}
    \fmflabel{$\bar{\mathrm{t}}$}{o2}
    \fmflabel{$\mathrm{t}$}{o1}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION - Quark-antiquark annihilation + FSR
\begin{fmfpicture}{-8,15}{15,18}{qq-ttbar-fsr} % padding (LTRB)
  \begin{fmfgraph*}(120,75) % dimensions (WH)
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o,o1}
    \fmfshift{2 up}{o}
    \fmfshift{6 right}{o}
    % main
    \fmf{fermion}{i1,v1,i2}
    \fmf{gluon,label=$g$,label.side=right,label.dist=10}{v2,v1}
    \fmf{phantom}{o2,v2,o1}
    \fmffreeze
    \fmf{fermion}{o2,v2,v,o1}
    \fmf{gluon,t=0}{v,o}
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
    \fmflabel{t}{o1}
    \fmflabel{$g$}{o}
    %\fmfv{decor.shape=circle,decor.filled=full,decor.size=3.5,f=(.7,,.1,,.1)}{v}
  \end{fmfgraph*}
\end{fmfpicture}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%% TTBAR PRODUCTION + DECAY %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% TTBAR PRODUCTION + DECAY
\begin{fmfpicture}{4,14}{35,17}{qq-ttbar-decay} % padding (LTRB)
  \begin{fmfgraph*}(160,150) % dimensions (WH)
    \fmfset{arrow_len}{3.6mm}
    % external vertices
    \fmfstraight
    \fmfleft{d,i2,i1,d} % add dummies 'd' for spacing
    \fmfright{o6,o5,o4,o3,o2,o1}
    \fmfshift{2 up}{i1}
    \fmfshift{2 down}{i2}
    %\fmfshift{8 left}{o1,o6} % shift b quarks left
    % qq -> g
    \fmf{fermion,t=1.4}{i2,vg,i1}
    \fmf{gluon,t=1.4}{vtt,vg} % gluon s-channel
    % ttbar
    \fmf{fermion,l.s=left,label={$\mathrm{t}$}}{vtt,v1}
    \fmf{fermion,l.s=left,label={$\overline{\mathrm{t}}$}}{v2,vtt}
    % bbbar
    \fmf{fermion,t=0.6}{v1,o1}
    \fmf{fermion,t=0.6}{o6,v2}
    \fmffreeze
    % W -> qq / lnu
    \fmf{boson,t=1.2,label=W$^+$,l.d=5,l.s=left}{v2,w2} % W boson
    \fmf{boson,t=1.2,label=W$^-$,l.d=5,l.s=right}{v1,w1} % W boson
    \fmf{fermion,t=1}{o3,w1,o2} % W decay
    \fmf{fermion,t=1}{o5,w2,o4} % W decay
    \fmf{phantom,t=0.05}{w1,w2} % pull decay vertices together
    % labels
    \fmfv{l.a=155,l.d=4,l=$q$}{i1}
    \fmfv{l.a=-155,l.d=5,l=$\overline{q}$}{i2}
    \fmfv{l.a=25,l.d=5,l=b}{o1}
    \fmfv{l.a=-25,l.d=5,l=$\overline{\mathrm{b}}$}{o6}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$\ell^-$} / $\overline{q}'$}{o2}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{\nu}_\ell$} / $q$}{o3}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$q'$} / $\ell^+$}{o4}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{q}'$} / $\nu_\ell$}{o5}
  \end{fmfgraph*}
\end{fmfpicture}

% TTBAR PRODUCTION + DECAY (round)
\begin{fmfpicture}{4,14}{35,17}{qq-ttbar-decay-round} % padding (LTRB)
  \begin{fmfgraph*}(160,150) % dimensions (WH)
    \fmfset{arrow_len}{3.6mm}
    % external vertices
    \fmfleft{d,i2,i1,d} % add dummies 'd' for spacing
    \fmfright{o6,o5,o4,o3,o2,o1}
    \fmfshift{2 up}{i1}
    \fmfshift{2 down}{i2}
    \fmfshift{4 left}{o1,o6} % shift b quarks left
    % qq -> g
    \fmf{fermion,t=1.1}{i2,vg,i1}
    \fmf{gluon,t=1.1}{vtt,vg} % gluon s-channel
    % ttbar
    \fmf{fermion,l.s=left,label={$\mathrm{t}$}}{vtt,v1}
    \fmf{fermion,l.s=left,label={$\overline{\mathrm{t}}$}}{v2,vtt}
    % bbbar
    \fmf{fermion,t=0.5}{v1,o1}
    \fmf{fermion,t=0.5}{o6,v2}
    \fmffreeze
    % W -> qq / lnu
    \fmf{boson,t=1.1,label=W$^+$,l.d=5,l.s=left}{v2,w2} % W boson
    \fmf{boson,t=1.1,label=W$^-$,l.d=5,l.s=right}{v1,w1} % W boson
    \fmf{fermion,t=1}{o3,w1,o2} % W decay
    \fmf{fermion,t=1}{o5,w2,o4} % W decay
    \fmf{phantom,t=0.2}{w1,w2} % pull decay vertices together
    %\fmf{phantom,t=0.05}{w1,o2,o5,w2} % pull decay vertices to the right
    % labels
    \fmfv{l.a=155,l.d=4,l=$q$}{i1}
    \fmfv{l.a=-155,l.d=5,l=$\overline{q}$}{i2}
    \fmfv{l.a=25,l.d=5,l=b}{o1}
    \fmfv{l.a=-25,l.d=5,l=$\overline{\mathrm{b}}$}{o6}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$\ell^-$} / $\overline{q}'$}{o2}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{\nu}_\ell$} / $q$}{o3}
    \fmfv{l.a=20,l.d=6,l=\makebox[3.1mm][l]{$q'$} / $\ell^+$}{o4}
    \fmfv{l.a=-20,l.d=6,l=\makebox[3.1mm][l]{$\overline{q}'$} / $\nu_\ell$}{o5}
  \end{fmfgraph*}
\end{fmfpicture}

\end{document}

Click to download: ttbar.tex • ttbar.pdf
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