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System-size dependence of particle-ratio fluctuations in Pb+Pb collisions at 158A GeV

New measurements by the NA49 experiment of the centrality dependence of event-by-event fluctuations of the particle yield ratios (K+ + K−)/(π+ + π−), (p + bar-p)/(π+ + π−), and (K+ + K−)/(p + bar-p) are presented for Pb+Pb collisions at 158A GeV. The absolute values of the dynamical fluctuations of these ratios, quantified by the measure σdyn, increase by about a factor of two from central to semiperipheral collisions. Multiplicity scaling scenarios are tested and found to apply for both the centrality and the previously published energy dependence of the (K+ + K−)/(π + + π−) and (p + bar-p)/(π+ + π−) ratio fluctuations. A description of the centrality and energy dependence of (K+ + K−)/(p + bar-p) ratio fluctuations by a common scaling prescription is not possible since there is a sign change in the energy dependence.

NA49; SPS; system-size; particle-ratio; fluctuation; critical endpoint

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