\begin{table}%t2
\par
%\centering
\par
\caption{NC 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{tb2}}
\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&  0&  0&  0&  1&  3\\
(740$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$ &  $6\times 10^{-2}$   &  0.1&  0.2&  0.6&  1.2\\
 2 & $N_{\rm d}$& 0&  0&  0&  0&  0&  1\\
(740$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$ & $5\times 10^{-2}$    &  0.1&  0.2&  0.5&  1.0\\
 3 & $N_{\rm d}$& 0&  0&  0&  0&  0&  2\\
(728$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$& $5\times 10^{-2}$  &  0.1&  0.2&  0.5&  1.0\\
 4 & $N_{\rm d}$& 0&  0&  0&  0&  0&  1\\
(726$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$& $6\times 10^{-2}$  &  0.1&  0.2&  0.6&  1.1\\
 5 & $N_{\rm d}$& 0&  0&  0&  0&  1&  2\\
(666$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$&  $5\times 10^{-2}$  &  0.1&  0.2&  0.5& 0.9\\
 6 & $N_{\rm d}$& 0&  1&  1&  1&  2&  2\\
(786$t$) &$N_{{\rm bk}}$&  $1\times 10^{-2}$&  $5\times 10^{-2}$  &  0.1&  0.2&  0.5&  1.0\\
 7 & $N_{\rm d}$& 0&  0&  0&  0&  0&  0\\
(364$t$) &$N_{{\rm bk}}$&  $4\times 10^{-3}$&  $2\times 10^{-2}$&  $4\times 10^{-2}$&  0.1&  0.2&  0.4\\
 8 & $N_{\rm d}$& 0&  0&  0&  1&  1&  1\\
(364$t$) &$N_{{\rm bk}}$&  $4\times 10^{-3}$&  $2\times  10^{-2}$&  $4\times 10^{-2}$&  0.1&  0.2&  0.4\\
 \hline
 $\Sigma_1^8$ & $N_{\rm d}$& 0&  1&  1&  2&  5&  12\\
$\bar M=639t$ &$N_{{\rm bk}}$&  0.07&  0.35& 0.7& 1.4 & 3.5&  7.0\\
\hline
\end{tabular}
\end{table}