Self-affine fluctuations of pions and protons and nonthermal phase transition in hadron–nucleus interactions

The paper reports a study revealing self-affine fluctuations in pion, proton, and compound multiplicity (of pions combined with protons) spectra obtained from the interactions of 350 GeV pions with AgBr nuclei. The study is performed in the transformed two-dimensional phase space of the emission and azimuthal angles using the factorial moment methodology and the concept of the Hurst exponent. Evidence of a nonthermal phase transition is obtained for self-affine fluctuations of pions along with an indication for such a regime to be seen in similar fluctuations of proton and compound multiplicity distributions. The study bridges the anisotropic nature of the multiparticle production process and an evidence of the nonthermal phase transition with similar earlier findings from hadron–hadron and nucleus–nucleus interactions and shows the same effects to be peculiar features of the multiplicity distributions of the different species of particles produced. All this brings important information about the underlying dynamics of the hadroproduction process.PACS Nos.: 25.80.Hp, 24.60.Ky, 13.85.–t