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\begin{document}
\begin{tabular}{l r@{$\ \pm \ $}l r@{$\ \pm \ $}l l r@{$\ \pm \ $}l r@{$\ \pm \ $}l}
\hline
Fit component           & \multicolumn{4}{c}{ $ B\xspace\xspace^\pm\xspace\rightarrow\xspace D\xspace K\xspace\xspace^\pm\xspace$ \xspace selection} & & \multicolumn{4}{c}{ $ B\xspace\xspace^\pm\xspace\rightarrow\xspace D\xspace\pi\xspace\xspace^\pm\xspace$ \xspace selection} \\
\cline{2-5} \cline{7-10}
                        & \multicolumn{2}{c}{Long} & \multicolumn{2}{c}{Downstream} & & \multicolumn{2}{c}{Long} & \multicolumn{2}{c}{Downstream} \\
\hline
 $ B\xspace\xspace^\pm\xspace\rightarrow\xspace D\xspace K\xspace\xspace^\pm\xspace$ \xspace              & $702$ & $18$ & $1555$ & $39$ & & $   30$ & $  5$ & $   64$ & $7$ \\
 $ B\xspace\xspace^\pm\xspace\rightarrow\xspace D\xspace\pi\xspace\xspace^\pm\xspace$ \xspace             & $ 87$ & $ 9$ & $ 164$ & $13$ & & $10\,338$ & $106$ & $22\,779$ & $166$ \\
Combinatorial           & $ 59$ & $ 9$ & $ 133$ & $14$ & & $  103$ & $ 11$ & $  433$ & $25$ \\
Partially reconstructed & $ 38$ & $ 2$ & $  82$ & $ 3$ & & $  4.6$ & $0.1$ & $ 14.2$ & $0.1$ \\
\hline
\end{tabular}
\end{document}
