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\begin{document}
    
    \begin{tabular}{lccc}
      \hline
      Source & \multicolumn{3}{c}{Uncertainty (fs)} \\ 
             &  $ B\xspace\xspace^0_ s\xspace\xspace\xspace\!\rightarrow\xspace  K\xspace\xspace^+\xspace K\xspace\xspace^-\xspace$ \xspace &  $ B\xspace\xspace^0\xspace\!\rightarrow\xspace  K\xspace\xspace^+\xspace\pi\xspace\xspace^-\xspace$ \xspace &  $ B\xspace\xspace^0_ s\xspace\xspace\xspace\!\rightarrow\xspace \pi\xspace\xspace^+\xspace K\xspace\xspace^-\xspace$ \xspace \\
      \hline
      Cross contamination                 &  4.8   &  1.3   &  6.0    \\
      Tracking efficiency                 & 2.8 & 2.8 & 2.8 \\
      Mass model                          & 1.1 & 2.5 & 6.7 \\
      $B_{c}^{+}$ contamination            & 1.1 & -- & 1.1 \\
      Non-parametric decay time modelling  & 0.8 & 1.6 & 6.7 \\
      Production asymmetry                & 3.0 &  --   &  --   \\
      Effective lifetime interpretation   & 1.2 & --  & --  \\
      Remaining uncertainties & 0.8 & 0.6 & 3.7\\
      \hline
      Total                               & 6.7 & 4.3 & 12.2 \\
      \hline
    \end{tabular}
    \label{tab:syst}
  
\end{document}
