\begin{table}%t2
%\centering
\par
\caption{Number of events before and after cuts, for the 
Mrk~421 data sets.
$N_\sigma$ is calculated after correcting for the $\sim $$80\%$ data acquisition
efficiency.
\label{results421tab}}
\begin{tabular}{llllllll}
\hline\hline
 &  & \multicolumn{3}{c}{Number of events} & Significance & Signal-to-noise & Excess\\
Data set & Cut & $N_{\rm \scriptsize{On}}$ & 
$N_{\rm \scriptsize{Off}}$ & 
$N_{\rm \scriptsize{On}}-N_{\rm \scriptsize{Off}}$ 
&  $N_\sigma$ & 
$\frac{N_{\rm \scriptsize{On}}-N_{\rm \scriptsize{Off}}}{N_{\rm \scriptsize{Off}}}~{\rm [\%]}$
& ${\rm [\gamma/{\rm min}]}$\\
\hline 
SP ($17.8~{\rm h}$) & Raw data & $1~575~396$ & $1~557~192$ & $18~204$ &  & & \\
& Software trigger & $1~056~705$ & $1~044~811$ & $11~894$ & 
$7.1$ & $1.1$ & $11.1$\\
& All cuts & $276~057$ & $270~113$ & $5~944$ & $7.1$ & $2.2$ & $5.6$\\
\hline
DP ($12.9~{\rm h}$) & Raw data & $983~550$ & $961~257$ & $22~293$ &  &  & \\
& Software trigger & $532~883$ & $523~661$ & $9~222$ & $8.1$ & 
$1.8$ & $11.9$\\
& All cuts & $113~507$ & $106~904$ & $6~603$ & $12.8$ & $6.2$ & $8.5$\\
\hline
SPV ($8.2~{\rm h}$) & Raw data & $621~243$ & $604~926$ & $16~317$ & &  &\\
& Software trigger & $410~429$ & $401~791$ & $8~638$ & $8.5$ & 
$2.1$ & $18.3$\\
& All cuts & $62~914$ & $57~551$ & $5~363$ & $13.9$ & $9.3$ & $11.8$\\
\hline  
All data ($38.9~{\rm h}$) & Raw data & $3~180~189$ & $3~123~375$ & $56~814$ & &  &\\
& Software trigger & $2~000~017$ & $1~970~264$ & $29~754$ & 
$13.1$ & $1.5$ & $12.7$\\
& All cuts & $452~478$ & $434~568$ & $17~910$ & $16.9$ & $4.1$ & $7.7$\\
\hline
\end{tabular}
\end{table}