diagrams.tex

\documentclass[12pt, parskip=full]{scrartcl}

\usepackage{tikz}

\usetikzlibrary{arrows.meta}
\usetikzlibrary{decorations.markings}

\tikzset{
    quarkline/.style={
        decoration={
            markings,
            mark=at position 0.7 with {\arrow{Latex}},
        },
        postaction={
            decorate,
        },
    },
    meson/.style={
        fill,
        circle,
        inner sep=0.5mm,
    },
}

\newcommand\helper[4]{
    \node[meson] (A) at (#1) {};
    \node[meson] (B) at (#2) {};
    \node[meson] (C) at (#3) {};
    \node[meson] (D) at (#4) {};

    \draw[dashed] (0, -1) node[below] {\small $t_\mathrm{so}$} -- (0, 5);
    \draw[dashed] (1, -1) node[below] {\small $t_\mathrm{so}+1$} -- (1, 5);
    \draw[dashed] (5, -1) node[below] {\small $t_\mathrm{si}$} -- (5, 5);
    \draw[dashed] (6, -1) node[below] {\small $t_\mathrm{si}+1$} -- (6, 5);
}

\newcommand\jitter[1]{
    \begin{tikzpicture}
        #1{0, 4}{5, 4}{0, 0}{5, 0}
    \end{tikzpicture}

    \begin{tikzpicture}
        #1{0, 4}{6, 4}{0, 0}{6, 0}
    \end{tikzpicture}

    \begin{tikzpicture}
        #1{1, 4}{5, 4}{1, 0}{5, 0}
    \end{tikzpicture}

    \begin{tikzpicture}
        #1{1, 4}{6, 4}{1, 0}{6, 0}
    \end{tikzpicture}
}

\newcommand\diagrammCross[4]{
    \helper{#1}{#2}{#3}{#4}
    \draw[quarkline] (A) -- (B);
    \draw[quarkline] (B) -- (C);
    \draw[quarkline] (C) -- (D);
    \draw[quarkline] (D) -- (A);
}

\newcommand\diagrammBox[4]{
    \helper{#1}{#2}{#3}{#4}
    \draw[quarkline] (A) -- (B);
    \draw[quarkline] (B) -- (D);
    \draw[quarkline] (D) -- (C);
    \draw[quarkline] (C) -- (A);
}

\newcommand\diagrammDirect[4]{
    \helper{#1}{#2}{#3}{#4}
    \draw[quarkline, out=20,  in=160] (A) to (B);
    \draw[quarkline, out=-160, in=-20] (B) to (A);
    \draw[quarkline, out=20,  in=160] (C) to (D);
    \draw[quarkline, out=-160, in=-20] (D) to (C);
}

\newcommand\diagrammVaccum[4]{
    \helper{#1}{#2}{#3}{#4}
    \draw[quarkline, out=290,  in=70] (A) to (C);
    \draw[quarkline, out=110, in=250] (C) to (A);
    \draw[quarkline, out=290,  in=70] (B) to (D);
    \draw[quarkline, out=110, in=250] (D) to (B);
}





\begin{document}

\section{Cross}

\jitter\diagrammCross

\section{Box}

\jitter\diagrammBox

\section{Direct}

\jitter\diagrammDirect

\section{Vacuum}

\jitter\diagrammVaccum

    
\end{document}