  Crosscorrelation of the outputs of two Gravitational Wave (GW) detectors has
recently been proposed [1] as a method for detecting statistical association
between GWs and Gamma Ray Bursts (GRBs). Unfortunately, the method can be
effectively used only in the case of stationary noise. In this work a different
crosscorrelation algorithm is presented, which may effectively be applied also
in non-stationary conditions for the cumulative analysis of a large number of
GRBs. The value of the crosscorrelation at zero delay, which is the only one
expected to be correlated to any astrophysical signal, is compared with the
distribution of crosscorrelation of the same data for all non-zero delays
within the integration time interval. This background distribution is gaussian,
so the statistical significance of an experimentally observed excess would be
well-defined.
  Computer simulations using real noise data of the cryogenic GW detectors
Explorer and Nautilus with superimposed delta-like signals were performed, to
test the effectiveness of the method, and theoretical estimates of its
sensitivity compared to the results of the simulation. The effectiveness of the
proposed algorithm is compared to that of other cumulative techniques, finding
that the algorithm is particularly effective in the case of non-gaussian noise
and of a large (100-1000s) and unpredictable delay between GWs and GRBs.
