Event texture search for critical fluctuations in Pb plus Pb collisions

NA44 uses a 512 channel Si pad array covering 1.5 < eta < 3.3 to study charged hadron production in 158 A GeV Pb+Pb collisions at the CERN SPS. We apply a multiresolution analysis, based on a Discrete Wavelet Transformation, to probe the texture of particle distributions event-by-event, by simultaneous localization of features in space and scale. Scanning a broad range of multiplicities, we look for possible critical behaviour in the power spectra of local density fluctuations. The data axe compared with detailed simulations of detector response, using heavy ion event generators, and with a reference sample created via event mixing. An upper limit is set on the probability and magnitude of dynamical fluctuations