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Puzzles in statistical hadron-gas treatment of systems created in proton-proton reactions at CERN SPS
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Europe/Zurich
CERN
CERN
Description
We analyze the newest data from NA61/SHINE Collaboration which include the 4π-yields of p, Λ, and φ-mesons produced in proton-proton (p+p) reactions at the CERN SPS energies √sNN = 6.3−17.3 GeV. The canonical ensemble hadron resonance gas model is used with exact conservation of net baryon number B = 2, electric charge Q = 2, and strangeness S = 0. The chemical freeze-out parameters in p+p interactions are obtained and compared to those in central nucleus-nucleus collisions.
We find several serious problems of the statistical model treatment of p+p reactions at the CERN SPS. An inclusion of the φ-meson multiplicities to the statistical model fit strongly influences a quality of the fit and makes it much worse (φ-meson puzzle). The data on event-by-event multiplicity fluctuations reveal a necessity of large non-statistical fluctuations in the system created in p+p inelastic reactions. The CE fit does not give any advantage over the grand canonical ensemble results, i.e., there is no indications to existence of a single statistical system in p+p.
V.V. Begun, V. Vovchenko, M.I. Gorenstein, H. Stoecker