Net charge fluctuations in $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{NN}}=130\text{GeV}$

We present the results of charged particle fluctuations measurements in $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{NN}}=130\text{GeV}$ using the STAR detector. Dynamical fluctuations measurements are presented for inclusive charged particle multiplicities as well as for identified charged pions, kaons, and protons. The net charge dynamical fluctuations are found to be large and negative providing clear evidence that positive and negative charged particle production is correlated within the pseudorapidity range investigated. Correlations are smaller than expected based on model-dependent predictions for a resonance gas or a quark-gluon gas which undergoes fast hadronization and freeze-out. Qualitative agreement is found with comparable scaled $p+p$ measurements and a heavy ion jet interaction generation model calculation based on independent particle collisions, although a small deviation from the $1∕N$ scaling dependence expected from this model is observed.

Figure 1

(Color online) (a) Dynamical fluctuations ${\nu }_{+-,dyn}$ measured in $\mid \eta \mid ⩽0.5$ as a function of the collision centrality estimated with the total (uncorrected) multiplicity $M$ in $\mid \eta \mid <0.75$. Error shown are statistical only. Systematic error estimated to $5\%$. (b) $⟨N⟩{\nu }_{+-,dyn}$ measured in $\mid \eta \mid ⩽0.5$ vs $M$ (opened circles) compared to the charge conservation limit (dotted line), resonance gas expectation based on Ref. [5] (solid line), and HIJING calculation (solid squares). Errors shown are statistical only. Systematic error estimated to $10\%$.

Figure 2

(Color online) Fluctuations ${\nu }_{+-,dyn}$ for the $6\%$ most central collisions as a function of the range of integrated pseudorapidities. Errors shown are statistical only. Systematic errors are estimated to range from $5\%$ at $\mid \eta \mid >0.4$ to $20\%$ at $\mid \eta \mid =0.1$. The expected limit due to charge conservation is shown as a dotted line.