\begin{table}%t1
\par
%\centering
\par
\caption{IBD class: number of events detected in
coincidence with the 8 GW events, for different durations of the
time window ($\delta t$), compared with the expectations from the
background. The effective LVD mass, $M$, at the time of each event
is also shown.\label{tb1}}
\begin{tabular}{ c  c c c c c c c }
\hline\hline
Ev. $n$. & & $ \delta t = 1$ s & $\delta t = 5$ s & $\delta t
= 10$ s & $\delta t = 20$ s &$\delta t = 50$ s&$\delta t
= 100$ s \\[-0.10cm]
($M$) & & & & & & & \\\hline
 1 & $N_{\rm d}$& 0&  1&  1&  1&  4&  6\\
(740$t$) &$N_{{\rm bk}}$&  $5\times 10^{-2}$ &  0.2&  0.5&  1.0&  2.4&  4.8\\
 2 & $N_{\rm d}$& 0&  0&  0&  1&  4&  7\\
(740$t$) &$N_{{\rm bk}}$&  $5\times 10^{-2}$ &  0.2&  0.5&  1.0&  2.5&  4.9\\
 3 & $N_{\rm d}$& 0&  1&  1&  1&  2&  6\\
(728$t$) &$N_{{\rm bk}}$&  $4\times 10^{-2}$ &  0.2&  0.4&  0.9&  2.1&  4.3\\
 4 & $N_{\rm d}$& 0&  0&  0&  0&  1&  2\\
(726$t$) &$N_{{\rm bk}}$&  $5\times 10^{-2}$ &  0.2&  0.5&  0.9&  2.3&  4.6\\
 5 & $N_{\rm d}$& 0&  0&  1&  3&  4& 11\\
(666$t$) &$N_{{\rm bk}}$&  $3\times 10^{-2}$&  0.2&  0.3&  0.7&  1.7&  3.4\\
 6 & $N_{\rm d}$& 0&  0&  0&  0&  1&  2\\
(786$t$) &$N_{{\rm bk}}$&  $4\times 10^{-2}$&  0.2&  0.4&  0.9&  2.2&  4.4\\
 7 & $N_{\rm d}$& 0&  1&  1&  2&  2&  2\\
(364$t$) &$N_{{\rm bk}}$&  $2\times 10^{-2}$&  0.1&  0.2&  0.3&  0.8&  1.6\\
 8 & $N_{\rm d}$& 0&  0&  0&  0&  0&  0\\
(364$t$) &$N_{{\rm bk}}$&  $2\times 10^{-2}$&  0.1&  0.2&  0.3&  0.8&  1.6\\
 \hline
 $\Sigma_1^8$ & $N_{\rm d}$& 0&  3&  4&  8&  18&  36\\
$\bar M=639t$ &$N_{{\rm bk}}$&  0.3&  1.5& 3.0& 5.9& 14.9&  29.7\\
\hline
\end{tabular}
\end{table}