K/pi Fluctuations at Relativistic Energies

Abstract

We report results for K/π fluctuations from Au+Au collisions at √ sNN = 19.6, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. Our results for K/π fluctuations in central collisions show little dependence on the incident energies studied and are on the same order as results observed by NA49 at the Super Proton Synchrotron in central Pb+Pb collisions at √ sNN = 12.3 and 17.3 GeV. We also report results for the collision centrality dependence of K/π fluctuations as well as results for K + /π + , K − /π − , K + /π − , and K − /π + fluctuations. We observe that the K/π fluctuations scale with the multiplicity density, dN/dη, rather than the number of participating nucleons.

Energy dependence of particle ratio fluctuations in central Pb+Pb collisions from $\sqrt{s_{_{NN}}} =$~6.3 to 17.3 GeV

“…Recently, the STAR collaboration has reported preliminary results for non-statistical K/π fluctuations in central Au+Au collisions in the RHIC energy range from √ s N N = 19.6 to 200 GeV [24]. The reported results for 19.6 GeV are in agreement with the values quoted here for √ s N N = 17.3 GeV, within statistical errors.…”

New results on event-by-event ratio fluctuations in Pb+Pb collisions at CERN SPS energies

“…The scaling properties of σ dyn found for the energy dependence above can thus be further tested by an analysis at fixed energy, only varying the system size. This has been done before by STAR [14] for (K + + K − )/(π + + π − ) fluctuations at two higher energies, and an increase of σ dyn when going to peripheral collisions was observed. All three ratios studied by NA49 show a similar increase in the magnitude of σ dyn when going to peripheral collisions.…”

Number-ratio fluctuations in high-energy particle production

“…Regarding K-to-π fluctuations, an approximate 1 〈M〉 -dependence has been observed in recent Au+Au data at 200 and 62.4 GeV from the STAR-collaboration [3].…”