The equation of state of baryon-symmetric hadronic matter with hard-sphere interactions is studied. It is assumed that mesons M are pointlike, but baryons B and antibaryons (B) over bar have the same hard-core radius r(B). Three possibilities are considered: (1) the BB and BB interactions are the same; (2) baryons do not interact with antibaryons; (3) the B (B) over bar, M (B) over bar, and MB interactions are negligible. By choosing the parameter r(B) = 0.3-0.6 fm, we calculate the nucleon to pion ratio as a function of temperature and perform the fit of hadron yields measured in central Pb+Pb collisions at root s(NN) = 2.76 TeV. New nontrivial effects in the interacting hadron resonance gas at temperatures 150-200 MeV are found.
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