Negative binomial fits to multiplicity distributions from central collisions of (sup 16)O + Cu at 14.6A GeV/c and intermittency

摘要

An 'intermittency' analysis of charged particle multiplicity data from the target multiplicy array (TMA) in central collisions of (sup 16)O+Cu at 14.6 A(times)GeV/c has been published by the AGS-E802 collaboration. The centrality cut was made using the Zero degree Calorimeter and requiring that the forward energy be less than one projectile nucleon (i.e. T(sub ZCAL) <13.6 GeV). In agreement with previous measurements, an apparent power-law growth of Normalized Factorial moments with decreasing pseudorapidity interval was observed in the range 1.0(= or >)(delta)(eta)(= or >)0.1. In the present work, multiplicity distributions in individual pseudorapidity bins are presented for the same data. These distributions are excellently fit by Negative Binomial Distributions (NBD) in all (delta)(eta) bins, allowing, for the first time, a systematic formulation of the subject of 'intermittency' in terms of distributions, rather than 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 (sup 16)O+Cu collisions is found to exhibit an apparently linear increase with the (delta)(eta) interval, albeit with a much steeper slope than for the other reactions, and a non-zero intercept, k(0)(not equal to)0. True intermittency, (xi) --> 0, would occur if the intercept k(0) --> 0, which is not observed in any experiment. The correlation length for central (sup 16)O+Cu collisions, although smaller than expected, is quite finite and can be measured - which means that a length scale exists in these collisions and therefore there is no intermittency in the multiplicity fluctuations.