Event-by-event fluctuations of the kaon to pion ratio in central Pb+Pb collisions at 158 GeV per Nucleon

TL;DR

This paper measures event-by-event fluctuations in the kaon to pion ratio in central Pb+Pb collisions at 158 GeV per nucleon, finding very small non-statistical fluctuations that could relate to QCD phase transitions.

Contribution

It provides the first measurement of strange particle fluctuation in heavy-ion collisions, setting upper limits on non-statistical fluctuations related to QCD phase transitions.

Findings

Non-statistical fluctuations are very small.

An upper limit on fluctuations related to phase transitions was established.

First measurement of kaon to pion ratio fluctuations in such collisions.

Abstract

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine non-statistical fluctuations, perhaps related to a first or second order QCD phase transition. Such fluctuations are shown to be very small.