Marlene Nahrgang, Tim Schuster, Michael Mitrovski, Reinhard Stock, Marcus Bleicher
We explore the potential of net-baryon, net-proton and net-charge kurtosis measurements to investigate the properties of hot and dense matter created in relativistic heavy-ion collisions. Contrary to calculations in a grand canonical ensemble we explicitly take into account exact electric and baryon charge conservation on an event-by-event basis. This drastically limits the width of baryon fluctuations. A simple model to account for this is to assume a grand-canonical distribution with a sharp cut-off at the tails. We present baseline predictions of the energy dependence of the net-baryon, net-proton and net-charge kurtosis for central ($b\leq 2.75$ fm) Pb+Pb/Au+Au collisions from $E_{lab}=2A$ GeV to $\sqrt{s_{NN}}=200$ GeV from the UrQMD model. While the net-charge kurtosis is compatible with values around zero, the net-baryon number decreases to large negative values with decreasing beam energy. The net-proton kurtosis becomes only slightly negative for low $\sqrt{s_{NN}}$.
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http://arxiv.org/abs/0903.2911
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