Revealing intermittency in nuclear multifragmentation with 4π detectors

The distortion on the intermittency signal, due to detection efficiency and to the presence of preequilibrium emitted particles, is studied in a schematic model of nuclear multifragmentation. A clear and genuine intermittency signal is generated by means of a percolating system, which is assumed to be in a region around the critical one. Mixing of events is considered to simulate the experimental conditions. The efficiency is schematized by a simple function of the fragment size, and the presence of preequilibrium particles is simulated by an additional noncritical fragment source. No selection on the events is considered, and therefore all events are used to calculate the moments. It is found that, despite the absence of event selection, the intermittency signal is not too much sensitive to the distortion due to the apparatus efficiency, while the inclusion of preequilibrium particles in the moment calculation can substantially reduce the strength of the signal. Preequilibrium particles should therefore be carefully separated from the rest of the detected fragments, before the intermittency analysis on experimental charge or mass distributions is carried out. © 1993 The American Physical Society.