\begin{tikzpicture}[y=-1cm,->,>=stealth',shorten >=1pt, scale=1.5]
  \definecolor{red}{RGB}{221,42,43}
  \definecolor{green}{RGB}{132,184,24}
  \definecolor{blue}{RGB}{0,72,112}
  \definecolor{orange}{RGB}{192,128,64}
  \definecolor{gray}{RGB}{107,108,110}
  \colorlet{black}{gray}

  \shadedraw [ball color=gray!5] (4,4) circle (1.5cm);

  \shadedraw [ball color=blue] (3.4,4.8) circle (0.22444cm);
  \shadedraw [ball color=red] (4.6,4.8) circle (0.22444cm);
  \shadedraw [ball color=blue] (3.4,3.2) circle (0.22444cm);
  \shadedraw [ball color=red] (4.6,3.2) circle (0.22444cm);

  \draw[black] (3.7,4.8) -- (4.3,4.8);
  \draw[black] (5,4.9) -- (5.9,5.1);
  \draw[black] (3.7,3.2) -- (4.3,3.2);
  \draw[black] (5,3.1) -- (5.9,2.9);
  \draw[<->,black] (3.46,4) +(-71:0.74) arc (-71:71:0.74);

  \begin{scope}[xshift=7pt]
    \path (3.,4.1) node[text=blue,anchor=base west] {\Large $n$};
    \path (4.2,4.1) node[text=red,anchor=base west] {\Large $p$};
  \end{scope}

  \path (5.8,5.3) node[text=black,anchor=base west] {\Large $e^-$};
  \path (5.8,2.9) node[text=black,anchor=base west] {\Large $e^-$};

  \path (4.1,4.45) node[text=black,anchor=base west] {\large $\nu_L$};
  \path (4.1,3.75) node[text=black,anchor=base west] {\large $\overline{\nu_R}$};

\end{tikzpicture}%

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