  We have analyzed the joint charged particle to photon density correlations in
WA98 experiment at CERN-SPS in order to study the formation of the chirally
disoriented vacuum in Pb + Pb collisions at 158 AGeV. The method of analysis is
based on the event-by-event estimation of a set of robust observables which are
the ratios of normalized bivariate factorial moments corrected for many
efficiency factors. This is found to be a very powerful technique in
identifying, within the limits of the detector resolution, the events with the
localized charged particle to photon density fluctuations.
