Veto Analysis Marina Del Prete Corso di Dottorato dell’ Universita’ di Siena It is a gravewave? Or did something locally create this ? Seismometer Dark Fringe

We search for a transient like signal or burst event which could be a signal from a supernova event A burst waveform is not well known and there are many kind of techniques to search for “generic” burst signals. We have to face the problem of noise in the experimental apparatus which can mimic a GW signal. We have a Dark Fringe signal (where we expect to observe the event of supernova), and many environmental monitoring and auxiliary channels It can be convenient to apply a veto analysis

I have only a peak in Dark Fringe I have a peak in Dark Fringe and in the enviromental channel. It is a possible good event It is possible that the signal in the Dark Fringe is a glitch It can be appropriate to apply a Veto on the Signal in Dark Fringe Set a threshold on the event SNR for the Dark Fringe (SNR> 5) and the enviromental channels The second step is to check at each time what happens within some interval  t. Dark Fringe channel Enviromental channel

How to decide if it is a good idea to apply a veto analysis on a specific channel? There are three fundamental parameters…… N ntv = # events above threshold and vetoed by noise channel N nt = # events above threshold in the noise channel Use Percentage = 100 * ( N ntv / N nt ) N stv = # events above threshold and vetoed in Dark Fringe channel N st = # events above threshold in the Dark Fringe channel Veto Efficiency = 100 * (N stv / N st )  t = time window of vetoed analysis  t n = time interval between two peaks of noise channel <  t Dead time = (N nt *  t –  t n )/run time

 t = 0.3 sec  t = 0.6 sec Veto efficiency =0.65% Seism. at ModeCleaner Use perc = 90% High value of use percentage and low value of dead time It is appropriate to apply the veto analysis to this channel It is appropriate to apply a veto in a specific channel if we have a high value of use percentage (>50%) and a low value of the dead time (<1%)  t = 0.6 sec  t = 0.3 sec Veto efficiency =0.7% Seism. at Beam Splitter Use perc = 25% Low value of use percentage It is not appropriate to apply the veto analysis to this channel