Multiplicity distributions from central collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu at 14.6A GeV/c and intermittency

The E-802 Collaboration at the BNL-AGS has measured charged particle multiplicity distributions from central (ZCAL) collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu at 14.6A GeV/c as a function of the pseudorapidity interval δη≥0.1 in the range 1.2≤η≤2.2. The fluctuations of these distributions as a function of the pseudorapidity interval have been studied by the method of normalized factorial moments and also by directly fitting the measurements to negative binomial distributions (NBD). Excellent fits to NBD were obtained in all δη bins, allowing, for the first time, a systematic formulation of the subject of intermittency in terms of distributions to complement the description based on normalized factorial moments. In agreement with all previous measurements of NBD fits to multiplicity distributions in hadron and lepton reactions, the k parameter of the NBD fit for central ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu collisions is found to exhibit an apparently linear increase with the δη interval, albeit with a much steeper slope than for other reactions, and a nonzero intercept, k(0)≠0. The evolution of the NBD parameter k(δη) is used to determine the two-particle short-range rapidity correlation length for central ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu collisions, ξ=0.18±0.05, which is much shorter than the value ξ∼1–3 for hadron collisions, but this is a quantitative rather than a qualitative difference. These results lead to a simple and elegant explanation of the intermittency formalism, without resort to fractals, for all reactions, which demystifies intermittency—for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu central collisions, intermittency is nothing more than the apparent statistical independence of the multiplicity in small pseudorapidity bins, δη∼0.2, due to the surprisingly short two-particle rapidity correlation length.