\begin{table}%t4
%\centering
\par
\caption{Number of events before and after cuts for the Mrk~501 data sets. 
$N_\sigma$ is calculated after correcting for the $\sim $$80\%$ data acquisition
efficiency.
\label{results501tab}}
\begin{tabular}{lllllll}
\hline\hline
 &  & \multicolumn{3}{c}{Number of events} & Significance  & Excess\\
Data set & Cut & $N_{\rm \scriptsize{On}}$ & $N_{\rm \scriptsize{\rm Off}}$ & $N_{\rm \scriptsize{\rm On}}-N_{\rm \scriptsize{Off}}$ & $N_\sigma$ & ${\rm ({\rm min}^{-1})}$\\
\hline 
Year 2000 ($8.3~{\rm h}$) & Raw data& $616~194$ & $613~337$ & $2~857$ & &\\
& Software trigger & $362~863$ & $359~914$ & $2~949$ & $2.9$  & $5.9$\\
& All cuts & $73~034$ & $71~518$ & $1516$ & $3.4$ &  $3.1$\\  \hline
Year 2001 ($2.0~{\rm h}$) & Raw data& $130~820$ & $131~584$ & $-764$ & &\\
& Software trigger & $67~040$ & $67~410$ & $-370$ & $-0.9$ & $-3.1$\\
& All cuts & $13~957$ & $14~059$ & $-102$ & $-0.6$  & $-0.85$\\
 \hline
All data ($10.3~{\rm h}$) & Raw data& $747~014$ & $744~921$ & $2~093$ & &\\
& Software trigger & $429~903$ & $427~323$ & $2~580$ & $2.4$  & $4.2$\\
& All cuts & $86~991$ & $85~578$ & $1413$ & $2.9$ & $2.3$\\
\hline
\end{tabular}
\end{table}