Intermitten Cy at Intermediate Energies

Apart from some misunderstandings of this summer, recent developments have led to considerable progress in this controversial but challenging field. Intermittency is now established as an effect in at least two dimensions, where it has turned out to be stronger and cleaner than in one. The effect is strongest in Ih and e+e~ collisions. In hh collisions, where the energy range covered is the largest, the effect is stronger at intermediate then at high y/a. Next to parton showering, intermittency is very sensitive to the soft phase, which will have to be studied with large statistics at intermediate energies, where it is not overshadowed by hard effects. In terms of the space-time development of a scattering process, the intermittency phenomenon and the determination of its parameters are shown to give a genuine information on the nature of hadronization at large distances compared to the hard interaction region. As such, it is expected to be sentitive to the nuclear environment of a deep-inelastic electron collision. In recent years events have been observed containing high particle density “spikes” in rapidity space. Fig.la shows the JACEE event [1 ] at a pseudo-rapidity resolution of ¿77= 0 . 1 unit, with local fluctuations up to dn/Srj us 300 and with a signal to back­ ground ratio of about 1 :1 . The NA2 2 event [2 ] of Fig.lb contains a rapidity “spike” of dn/dy—100 at a rapidity resolution ¿>y=0.1. This corresponds to 60 times the average density in this experiment. Also UA5 [3] has reported “spikes” of dn/dq up to 30 (10 times average) as early as JACEE, but found these to be in agreement with a short range cluster Monte Carlo. No doubt, local density fluctuations exist. The question is whether they are of statistical or dynamical origin, whether the underlying probability density is continuous or intermittent. To study these, Bialas and Peschanski [4] have suggested to study the dependence of scaled factorial multiplicity moments * On leave of absence from Saclay, Service de Physique Théorique, France. 0375-9474/91/$03.50 © 1991 Elsevier Scicncc Publishers B.V. All rights reserved. 490c W. Kittcl, R, Peschanski I ¡ntennittency at intermediate energies