Search for the QCD critical point in nuclear collisions at 158A GeV at the CERN Super Proton Synchrotron (SPS)

• Published in: Physical review. C, Nuclear physics Nuclear physics, 2010-06, Vol.81 (6)
• Main Authors: Anticic, T., Kadija, K., Nicolic, V., Susa, T., Baatar, B., Kolesnikov, V. I., Malakhov, A. I., Melkumov, G. L., Barna, D., Fodor, Z., Laszlo, A., Palla, G., Sikler, F., Varga, D., Veres, G. I., Vesztergombi, G., Bartke, J., Kowalski, M., Rybicki, A., Betev, L.
• Format: Article
• Language: English
• Subjects: ACCELERATORS; ATOM COLLISIONS; ATOM-ATOM COLLISIONS; BARYON-BARYON INTERACTIONS; BARYONS; BOSONS; CAPTURE; CARBON; CERN; CERN SPS SYNCHROTRON; COLLISIONS; CORRELATIONS; CYCLIC ACCELERATORS; DIAGRAMS; ELEMENTARY PARTICLES; ELEMENTS; ENERGY RANGE; FERMIONS; FIELD THEORIES; FLUCTUATIONS; FORECASTING; FREEZING OUT; GEV RANGE; GEV RANGE 100-1000; HADRON-HADRON INTERACTIONS; HADRONS; INFORMATION; INTERACTIONS; INTERNATIONAL ORGANIZATIONS; LEAD; MASS; MESONS; METALS; NONMETALS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR REACTIONS; NUCLEI; NUCLEON-NUCLEON INTERACTIONS; NUCLEONS; PAIR PRODUCTION; PARTICLE INTERACTIONS; PARTICLE PRODUCTION; PHASE DIAGRAMS; PIONS; PIONS MINUS; PIONS PLUS; PROTON-NUCLEON INTERACTIONS; PROTON-PROTON INTERACTIONS; PROTONS; PSEUDOSCALAR MESONS; QUANTUM CHROMODYNAMICS; QUANTUM FIELD THEORY; SEMIMETALS; SEPARATION PROCESSES; SILICON; SYNCHROTRONS; VARIATIONS
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PHYSREVC.81.064907

Pion production in nuclear collisions at the Super Proton Synchrotron (SPS) is investigated with the aim to search, in a restricted domain of the phase diagram, for power laws in the behavior of correlations that are compatible with critical QCD. We analyzed interactions of nuclei of different sizes (p+p, C+C, Si+Si, Pb+Pb) at 158A GeV adopting, as appropriate observables, scaled factorial moments in a search for intermittent fluctuations in transverse dimensions. The analysis is performed for pi{sup +}pi{sup -} pairs with an invariant mass very close to the two-pion threshold. In this sector one may capture critical fluctuations of the sigma component in a hadronic medium, even if the sigma meson has no well-defined vacuum state. It turns out that for the Pb+Pb system the proposed analysis technique cannot be applied without entering the invariant mass region with strong Coulomb correlations. As a result the treatment becomes inconclusive in this case. Our results for the other systems indicate the presence of power-law fluctuations in the freeze-out state of Si+Si approaching in size the prediction of critical QCD.