Table 2: 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.
    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 $ $\frac{N_{\rm\scriptsize {On}}-N_{\rm\scriptsize {Off}}}{N_{\rm\scriptsize {Off}}}~{\rm [\%]}$ ${\rm [\gamma/{\rm min}]}$
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
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
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
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


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