# How to adjust length of bosons, feynmp/feynmf

I am having trouble making the length of three bosons the same. I've been working on this diagram for more than two weeks and just can't get the length to come out just right. Here is my code:

\documentclass{article}
\usepackage{feynmf}%%%{feynmp}
\usepackage{tikz}

\unitlength=1mm
\begin{document}

\begin{fmffile}{tree2}
\begin{fmfgraph*}(60,55)

\fmfleft{i0,i1,i2,i3,i4}
\fmfright{o0,o1,o2,o3,o4}
%%\fmf{fermion}{o1,i1}
\fmf{scalar, label=$A^0$, tension=.7,l.side=left}{i2,v2}
\fmf{scalar, label=$\vec{q}$, tension=.7,l.side=right}{i2,v2}
\fmf{phantom}{v2,o2}
\fmffreeze
\fmf{boson, label=$Z$, lab.side=left}{v3,o4}
\fmf{boson, label=$\vec{p_3}$, lab.side=right}{v3,o4}

\fmf{boson, label=$Z$ , lab.side=right}{v3,o2}
\fmf{boson, label=$\vec{p_2}$ , lab.side=left}{v3,o2}

\fmf{scalar, label=$H$, tension = .5, l.side=left}{v2,v3}
\fmf{scalar, label=$\vec{q}-\vec{p_1}$, tension = .5,l.side=right}{v2,v3}

\fmf{phantom}{i4,v3}
\fmffreeze
\fmf{boson, label=$\vec{p_1}$ , lab.side=right}{v2,o0}
\fmf{boson, label=$Z$ , lab.side=left}{v2,o0}

\fmflabel{$\mu$}{o0}
\fmflabel{$\nu$}{o2}
\fmflabel{$\rho$}{o4}

\end{fmfgraph*}
\end{fmffile}
\end{document}


Thank You!

-
Could you give the image you are trying to draw? – Dox Jun 22 '14 at 4:35
It's been added. I am trying to position bottom two bosons parallel to each other, and make them the same in length. Thank You! – soccerboyz9341 Jun 23 '14 at 0:54

It appears to me that the the two top Z bosons have the same length as the H. The solution is then to introduce a vertex similar to the one H -> ZZ. The 'process' at the bottom would then just be Z -> phantom phantom, or for simplicity Z -> phantom.

I checked on my machine that this gives the desired result.

The motivated reader can skip reading the code given below and try to find the implementation on his/her own.

\documentclass{article}
\usepackage{feynmf}%%%{feynmp}
\usepackage{tikz}

\unitlength=1mm
\begin{document}
\begin{fmffile}{tree2}
\begin{fmfgraph*}(60,55)

\fmfleft{i0,i1,i2,i3,i4}
\fmfright{o0,o1,o2,o3,o4}
%%\fmf{fermion}{o1,i1}
\fmf{scalar, label=$A^0$, tension=.7,l.side=left}{i2,v2}
\fmf{scalar, label=$\vec{q}$, tension=.7,l.side=right}{i2,v2}
\fmf{phantom}{v2,o2}
\fmffreeze
\fmf{boson, label=$Z$, lab.side=left}{v3,o4}
\fmf{boson, label=$\vec{p_3}$, lab.side=right}{v3,o4}

\fmf{boson, label=$Z$ , lab.side=right}{v3,o2}
\fmf{boson, label=$\vec{p_2}$ , lab.side=left}{v3,o2}

\fmf{scalar, label=$H$, tension = .5, l.side=left}{v2,v3}
\fmf{scalar, label=$\vec{q}-\vec{p_1}$, tension = .5,l.side=right}{v2,v3}

\fmf{phantom}{i4,v3}
\fmffreeze
% Changed end vertex
\fmf{boson, label=$\vec{p_1}$ , lab.side=right}{v2,v4}
\fmf{boson, label=$Z$ , lab.side=left}{v2,v4}
\fmf{phantom, label=Phant1, lab.side=left}{v4,o0}
\fmf{phantom, label=Phant2, lab.side=left}{v4,o1}

% Changed labeled vertex
\fmflabel{$\mu$}{v4}

\fmflabel{$\nu$}{o2}
\fmflabel{$\rho$}{o4}

\end{fmfgraph*}
\end{fmffile}
\end{document}

-
Welcome to TeX.SX! Would you like to add some code explaining what you did? – egreg Jun 25 '14 at 10:35
Thanks egreg for your suggestion! I added the code in the answer. :) – user22234 Jun 27 '14 at 15:32