Publisher’s Note: Proton-Number Fluctuation as a Signal of the QCD Critical End Point [Phys. Rev. Lett.PRLTAO0031-900791, 102003 (2003)]

We argue that the event-by-event fluctuation of the proton number is a meaningful and promising observable for the purpose of detecting the QCD critical end-point in heavy-ion collision experiments. The long range fluctuation of the order parameter induces a characteristic correlation between protons which can be measured. The proton fluctuation also manifests itself as anomalous enhancement of charge fluctuations near the end-point, which might be already seen in existing data.