Effects of Initial Density Fluctuations on Cumulants in Au+Au Collisions at 7.7 GeV Center-of-Mass Energy
Within the ultra-relativistic quantum molecular dynamics(UrQMD)model,the effect of initial density fluctuations,which caused by varying the minimum distance dmin between two nucleons in the initialization,on cumulants of the net-pro-ton multiplicity distribution in Au+Au collisions at √SNN=7.7 GeV is investigated.It is found that the density fluctuations in the initial state increase with the decrease of dmin from 1.6 to 1.0 fm.During the expand of fireball,the effect of initial density fluctuations on cumulants gradually reduced,while the influence of mean-field is remarkable.In the momentum space of the final state of the collision,the influence of dmin on the magnitude of the net-proton number fluctuation in a narrow pseudo-rapidity window(⊿η≤4)is negligible.However,in a broad pseudo-rapidity window(⊿η＞4),dmin obviously impacts the cumulant ratios of net-proton multiplicity.In the semi-center collision(b=5 fm),the effect of dmin is about 2～3 times than that of the mean-field.
heavy-ion collisioninitial density fluctuationtransport modelcumulants
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