On a Signature of Phase Transition in Heavy Ion Nuclear Matter

Some results of data analysis of hadron production in $$p + p$$ and $$A + A$$ collisions obtained in the framework of $$z$$ -scaling are discussed. A possible signature of phase transition in the matter created in central $${\text{Au}} + {\text{Au}}$$ collisions in the scaling regime is observed. The concept of the $$z$$ -scaling is based on the principles of self-similarity, locality and fractality of particle interactions at a constituent level. The self-similarity variable $$z$$ and the scaling function $$\psi (z)$$ are expressed via the experimentally measurable quantities and some model parameters characterizing the structure of colliding objects, fragmentation process and specific heat of the produced medium. The irregularities of fractal entropy and specific heat parameter $${{c}_{{{\text{AuAu}}}}}$$ observed in $$K_{S}^{0}$$ -meson production in $${\text{Au}} + {\text{Au}}$$ collisions at RHIC are considered as an indication of phase transition in nuclear matter.