Terence J. Tarnowsky, Gary D. Westfall
A study of the first four moments (mean, variance, skewness, and kurtosis) and their products ($\kappa\sigma^{2}$ and $S\sigma$) of the net-charge and net-proton distributions in Au+Au collisions at $\sqrt{\rm s_{NN}}$ = 7.7-200 GeV from HIJING simulations has been carried out. It is seen that a Poisson does not effectively describe the actual distributions of positive and negative particles (or protons and anti-protons). A discrete probability distribution that effectively describes the raw distributions is the negative binomial (or binomial) distribution (NBD/BD). The NBD/BD have been used to characterize particle production in high-energy particle and nuclear physics. Differences between $\kappa\sigma^{2}$ and the Poisson assumption of a factor of four (for net-charge) and 40% (for net-protons) can be accounted for by the NBD/BD. This is the first application of the NBD/BD to describe the behavior of the higher moments of net-charge and net-proton distributions in nucleus-nucleus collisions.
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http://arxiv.org/abs/1210.8102
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