Ttyjukl

I would like to understand how can I label edges of diagrams as at this picture:

I assume that it possible to label vertices and than move each label, but I do not know how. Can anyone gives some suggestions?

What I tried: label each vertex

begin{feynman}

    vertex (v1) {(cl)};

    vertex[right=0.5cm of v1] (v2) {(cl)};

    vertex[right=1cm of v2] (v3) {(cl)};

    vertex[right=0.5cm of v3] (v4) {(cl)};;

    diagram*{(v1)--(v2), (v2)--[half left](v3)--[half left](v2),(v3)--(v4)};

end{feynman}

It is awful. Then, I have tried to label edges:

begin{feynman}

        vertex (v1);

        vertex[right=0.5cm of v1] (v2);

        vertex[right=1cm of v2] (v3);

        vertex[right=0.5cm of v3] (v4);

        diagram*{(v1)--[edge label={(cl quad)}](v2), (v2)--[half left,edge label={(cl quad cl)}](v3)--[half left,edge label={(cl quad cl)}](v2),(v3)--[edge label={(quad cl)}](v4)};

    end{feynman}

It looks not so awful, but not perfect: labels are so far from edges.

I have kept the same structure as you by eliminating your labels and I have inserted them manually using nodes.... (a) (b) .... with cartesian coordinates that have all small labels and are closer to the ellipse.

documentclass[tikz]{article}

usepackage{tikz-feynman}

tikzfeynmanset{compat=1.0.0}

begin{document}



begin{tikzpicture}

begin{feynman}

        vertex (v1);

        vertex[right=0.5cm of v1] (v2);

        vertex[right=1cm of v2] (v3);

        vertex[right=0.5cm of v3] (v4);

        diagram*{(v1)--[edge label={{}}](v2),

         (v2)--[half left,edge label={}](v3)--[half left,edge label={}](v2),

         (v3)--[edge label={}](v4)};

end{feynman}

 node(a) at (.6,-.5) {small cl};

 node(b) at (1.35,-.5) {small cl};

 node(c) at (.6,.5) {small cl};

 node(d) at (1.35,.5) {small cl};

 node(e) at (-.11,.15) {small cl};

 node(f) at (2.1,.15) {small cl};

 end{tikzpicture}

end{document}

Using hardcoded coordinates like node(a) at (.6,-.5) {small cl}; in tikz is a deadly sin, this will break as soon as you change the tiniest thing.

• to move the labels on the horizontal lines to the start and end of the lines, use near start and near end




• to move the labels around the circle closer to the line, reduce the inner sep




• don't use inline math to make multi-letter things italic

% !TeX TS-program = lualatex

documentclass{article}

usepackage{tikz-feynman}



begin{document}



begin{tikzpicture}

begin{feynman}

        vertex (v1);

        vertex[right=0.5cm of v1] (v2);

        vertex[right=1cm of v2] (v3);

        vertex[right=0.5cm of v3] (v4);

        diagram*{

            (v1)--[edge label={textit{cl}},near start](v2), 

            (v2)--[half left,edge label={textit{clquad cl}},inner sep=1pt](v3)--[half left,edge label={textit{clquad cl}},inner sep=1pt](v2),

            (v3)--[edge label={textit{cl}},near end](v4)

        };

    end{feynman}

 end{tikzpicture}

end{document}

Alternatively without any manual intervention, one can let tikz-feynman do it's job:

% !TeX TS-program = lualatex

documentclass{article}

usepackage{tikz-feynman}



begin{document}



begin{tikzpicture}[inner sep=2pt]

    itshape

    begin{feynman}

        diagram[horizontal=a to f,small]{

            a--[edge label={cl},near start]b, 

            b -- [quarter right,edge label'={cl}] 

            c -- [quarter right,edge label'={cl}] 

            d -- [quarter right,edge label'={cl}] 

            e -- [quarter right,edge label'={cl}] 

            b,

            d--[edge label={cl},near end]f

        };

    end{feynman}

end{tikzpicture}



end{document}