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reproduce the STAR data for 0-10% central collisions and the PACIAE model is somewhat better than oth- ers. However all of the model results are higher than the STAR data for the 40-50% central collisions, therefore can not reproduce b as an exponential function of Δ η observed by STAR as shown in Fig. 3 (b). 

We have noted the mentions in [6] that “To avoid a bias in the FB correlation measurements, care was taken to use different pseudorapidity selection for the centrality determination which is also based on multiplicity. There- fore, the centrality determination for the FB correlation strength for Δ η =0.2, 0.4, and 0.6 is based on the mul- tiplicity in 0 . 5 < | η | < 1 . 0, while for Δ η =1.2, 1.4, 1.6, and 1.8, the centrality is obtained from | η | < 0 . 5. For Δ η =0.8 and 1.0, the sum of multiplicities from | η | < 0 . 3 and 0 . 8 < | η | < 1 . 0 is used for the centrality deter- mination.” So we follow STAR’s centrality determina- tion convention to repeat all of the PACIAE calcula- tions and draw Fig. 4 with these results. Comparing Fig. 4 with Fig. 2 (b) we see this complicated central- ity determination does not improve but even worsens the agreement between experiment and theory. That means STAR’s centrality determination convention may be needed for the experimental measurement of FB cor- relation strength but not for the theoretical calculation. 

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In this kind of theoretical calculations, each definite cen- trality curve in Fig. 4 is composed of b calculated at dif- ferent Δ η with different centrality determination, such kind of curve is not reasonable in theoretical physics. 

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Figure 5 gives the PACIAE model prediction for the charged particle FB multiplicity correlation strength in Pb+Pb collisions at √ s$_{NN}$ =5500 GeV. We can see that the FB multiplicity correlation strength in Pb+Pb col- 

