\documentclass[tikz,border=5pt]{standalone}
\usepackage{amsmath, amssymb, color}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
[
decoration={
markings,
mark=at position 0.25 with {\arrow[line width=1pt]{>}},
mark=at position 0.75 with {\arrow[line width=1pt]{>}},
}
]
\def\deltaaxis{0.025}
\def\contourradius{3.5}
\def\deltapolesnuclear{0.833}
\def\deltapolesphoton{1.666}
\def\deltapoleselectron{2.5}
\draw [ ->, line width=1.0 ] (-4,0) -- (4,0) node[ right, font=\large ] {$ \quad \mathcal{R}e \, \nu $};
\draw [ ->, line width=1.0 ] (0,-4) -- (0,4) node[ right, font=\large ] {$ \quad \mathcal{I}m \, \nu $};
\node [ font=\Large ] at ( -3.5, 3.85 ) {$ \Gamma_{ \mathrm{d} } = \Gamma_{ 1 } \oplus \Gamma_{ \mathrm{Wick} } \oplus \Gamma_{ 2 } $};
\path [ draw, blue, line width=1.0, postaction=decorate ] ( \contourradius, 0 ) arc ( 0 : 90 : \contourradius );
\path [ draw, blue, line width=1.0 ] ( 0, \contourradius ) -- ( -\deltaaxis - 0.01, \contourradius );
\node [ font=\Large ] at ( \contourradius - 0.5, \contourradius - 0.5 ) {$ \Gamma_{ 1 } $};
\path [ draw, blue, line width=1.0, postaction=decorate ] ( -\deltaaxis, -\contourradius ) arc ( 90 : 0.5 : -\contourradius );
\node [ font=\Large ] at ( -\contourradius + 0.5, -\contourradius + 0.5 ) {$ \Gamma_{ 2 } $};
\path [ draw, blue, line width=1.0, postaction=decorate ] ( -\contourradius - 0.05, -\deltaaxis ) -- ( \contourradius, -\deltaaxis );
\path [ draw, blue, line width=1.0 ] ( \contourradius, -\deltaaxis - 0.01) -- ( \contourradius, 0.0 );
\node [ font=\Large ] at ( \contourradius - 1.0, 0.4 ) {$ \Gamma_{ \mathrm{real} } $};
\path [ draw, blue, line width=1.0, postaction=decorate ] ( -\deltaaxis, \contourradius ) -- ( -\deltaaxis, -\contourradius );
\node [ font=\Large ] at ( 0.75, \contourradius/3 ) {$ \Gamma_{ \mathrm{Wick} } $};
\fill[ green!65!black ] ( -0.5, -\deltapolesnuclear ) circle (1.5pt);
\fill[ red!65!black ] ( -1.25, \deltapolesnuclear ) circle (1.5pt) ( -1.5, \deltapolesnuclear ) circle (1.5pt);
\node [ font=\large ] at ( -2.0, \deltapolesnuclear - \deltaaxis ) {$\cdots$};
\draw[ ->, line width=1.0, red!65!black ] ( -2.5, \deltapolesnuclear ) -- ( -4, \deltapolesnuclear );
\node [ font=\large ] at ( -4.75, \deltapolesnuclear ) {$ \mathrm{P}^{(+)}_{ \mathcal{N} } $};
\fill[ red!65!black ] ( 0.5, -\deltapolesnuclear ) circle (1.5pt) ( 1.25, -\deltapolesnuclear ) circle (1.5pt) ( 1.5, -\deltapolesnuclear ) circle (1.5pt);
\node [ font=\large ] at ( 2.0, -\deltapolesnuclear - \deltaaxis ) {$\cdots$};
\draw[ ->, line width=1.0, red!65!black ] ( 2.5, -\deltapolesnuclear ) -- ( 4, -\deltapolesnuclear );
\node [ font=\large ] at ( 4.75, -\deltapolesnuclear - \deltaaxis ) {$ \mathrm{P}^{(-)}_{ \mathcal{N} } $};
\fill [ red!45!blue ] ( \deltaaxis, -\deltapolesphoton ) circle (1.5pt);
\draw [ ->, line width=1.0, red!45!blue ] ( 0, \deltapolesphoton ) -- ( -4, \deltapolesphoton );
\node [ font=\large ] at ( -4.75, \deltapolesphoton ) {$ \mathrm{P}^{(+)}_{ \gamma } $};
\fill [ red!45!blue ] ( -\deltaaxis, \deltapolesphoton ) circle (1.5pt);
\draw [ ->, line width=1.0, red!45!blue ] ( 0, -\deltapolesphoton ) -- ( 4, -\deltapolesphoton );
\node [ font=\large ] at ( 4.75, -\deltapolesphoton ) {$ \mathrm{P}^{(-)}_{ \gamma } $};
\fill [ red!65!green ] ( \deltaaxis, \deltapoleselectron + 0.50 ) circle (1.5pt);
\draw [ red!65!green, line width=1.0 ] ( 0.5, \deltapoleselectron ) arc ( 92 : 268 : -0.25);
\draw [ red!65!green, line width=1.0 ] ( 0.0, \deltapoleselectron + 0.50 ) -- ( 0.5, \deltapoleselectron + 0.50 );
\draw [ ->, red!65!green, line width=1.0 ] ( 0.5, \deltapoleselectron ) -- ( -4.0, \deltapoleselectron );
\node [ font=\large ] at ( -4.75, \deltapoleselectron ) {$ \mathrm{P}^{(+)}_{ e } $};
\fill [ red!65!green ] ( 2.0, -\deltapoleselectron - 0.50 ) circle (1.5pt);
\draw [ red!65!green, line width=1.0 ] ( 1.5, -\deltapoleselectron ) arc ( 92 : 272 : 0.25);
\draw [ red!65!green, line width=1.0 ] ( 2.0, -\deltapoleselectron - 0.50 ) -- ( 1.5, -\deltapoleselectron - 0.50 );
\draw [ ->, red!65!green, line width=1.0 ] ( 1.5, -\deltapoleselectron ) -- ( 4.0, -\deltapoleselectron );
\node [ font=\large ] at ( 4.75, -\deltapoleselectron ) {$ \mathrm{P}^{(-)}_{ e } $};
\end{tikzpicture}
\end{document}