# Aligning propagators on feynmp

I want to align the propagators that go from the circle to the vertices p_3 and p_4

Here is my MWE:

\documentclass[amsmath,amssymb,aps,12pt,eqsecnum]{revtex4}
\usepackage[a4paper]{geometry}
\usepackage{slashed}
\usepackage{simplewick}
\usepackage{feynmp-auto}
\usepackage[pdftex]{graphicx}
\usepackage{textcomp}
\usepackage{gensymb}
\begin{document}
\begin{fmffile}{counterterms3}
\begin{fmfgraph*}(100,100)
\fmfbottom{i0,i1,i2,i3}
\fmftop{o1,o2}
\fmf{plain}{i1,v2}
\fmf{plain}{i2,v1}
\fmf{plain,left}{v2,v3}
\fmf{plain,right}{v1,v3}
\fmf{plain}{v3,o1}
\fmf{plain}{v3,o2}
\fmfv{label=$p_1$}{i1}
\fmfv{label=$p_2$}{i2}
\fmfv{label=$p_3$}{o1}
\fmfv{label=$p_4$}{o2}
\fmffreeze
\fmf{phantom}{v1,v2}
\fmf{plain,left}{v1,v2}
\fmf{plain,left}{v2,v1}
\fmf{dot}{v3}
\end{fmfgraph*}
\end{fmffile}
\end{document}


As you can see, the propagators from the circle go horizontal at the vertex with the dot, rather than going in the same direction as the propagators which lead to p_3 and p_4

• Can you explain more clearly how exactly you want to align them? Do you want them to not meet in a single vertex marked with the dot, but to have some offset from the vertex? – BartoNaz Jul 7 '16 at 10:56

You may make these curves parallel by playing with left and right.

\begin{fmfgraph*}(100,100)
\fmfbottom{i0,i1,i2,i3}
\fmftop{o1,o2}
\fmf{plain}{i1,v2}
\fmf{plain}{i2,v1}
\fmf{phantom,left}{v2,v3}
\fmf{phantom,right}{v1,v3}
\fmf{plain}{v3,o1}
\fmf{plain}{v3,o2}
\fmfv{label=$p_1$}{i1}
\fmfv{label=$p_2$}{i2}
\fmfv{label=$p_3$}{o1}
\fmfv{label=$p_4$}{o2}
\fmffreeze
\fmf{plain,left=1.45}{v2,v3}
\fmf{plain,right=1.45}{v1,v3}
\fmf{phantom}{v1,v2}
\fmf{plain,left}{v1,v2}
\fmf{plain,left}{v2,v1}
\fmf{dot}{v3}
\end{fmfgraph*}