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is introduced [23]. In the above equation, g stands for the geometrical (total) cross section percentage (or charged multiplicity percentage) used in the experimental deter- mination of centrality. R$_{A}$ = 1 . 12 A 1 / 3 + 0 . 45 fm is the radius of nucleus A . We have also used the centrality determination based on the charged multiplicity N$_{ch}$ in the central pseudorapidity window | η | < 1 to study the FB multiplicity correlation strength as a function of Δ η . 

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We compare the calculated charged particle pseudora- pidity distribution in specified centrality bin in Au+Au collisions at √ s$_{NN}$ =200 GeV with the corresponding PHOBOS data [22] in Fig. 1. Here the theoretical cen- trality are defined by impact parameter b$_{i}$ via Eq.(6). One sees that the PHOBOS data are well reproduced. 

The PACIAE model results of FB multiplicity corre- lation strength are shown in Fig. 2 (a) and (b) for the centrality determinations of the impact parameter b$_{i}$ and charged multiplicity N$_{ch}$ ( | η | < 1), respectively. One sees in Fig. 2 (a) that the theoretical results can reproduce the STAR data for 0-10% most central collisions. How- ever the theoretical results are all higher than the cor- responding STAR data for the 10-20%, 20-30%, 30-40%, and 40-50% most central collisions and those theoretical 

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results are closed to each other. That is because the FB multiplicity correlation in Au+Au collisions is mainly the statistical correlation steaming from the multiplic- ity fluctuation [14]. And the multiplicity fluctuation in those centralities defined by impact parameter are simi- lar to each other. 

Figure 2 (b) gives the FB correlation strength calcu- lated with the charged particle multiplicity ( | η | < 1) centrality determination together with the STAR data. We see in this panel that the STAR data are well re- produced by the PACIAE model for the 0-10%, 10-20%, and 20-30% central collisions. However, the PACIAE re- sults are higher than the corresponding STAR data for 30-40%, and 40-50% central collisions. The correlation strength approaches an exponential function of Δ η ob- served by STAR in 40-50% central collisions can not be reproduced especially. 

In Fig. 3 we compare the FB multiplicity correla- tion strength as a function of Δ η calculated by the wounded nucleon model [12], GMC code with a “toy” wounded-nucleon model, HSD transport approach [13], and PACIAE model with the STAR data for the 0-10% (panel(a)) and 40-50% central collisions (panel (b)). We see in Fig. 3 (a) that all of the four models can nearly 

