Hadron Production In High Energy Collisions Research Articles

Chemical freeze-out in Hawking-Unruh radiation and quark-hadron transition

The proposed analogy between hadron production in high-energy collisions and Hawking-Unruh radiation process in the black holes shall be extended. This mechanism provides a theoretical basis for the freeze-out parameters, the temperature ($T$) and the baryon chemical potential ($\mu$), characterizing the final state of particle production. The results from charged black holes, in which the electric charge is related to $\mu$, are found comparable with the phenomenologically deduced parameters from the ratios of various particle species and the higher-order moments of net-proton multiplicity in thermal statistical models and Polyakov linear-sigma model. Furthermore, the resulting freeze-out condition $\langle E\rangle/\langle N\rangle\simeq 1~$GeV for average energy per particle is in good agreement with the hadronization process in the high-energy experiments. For the entropy density ($s$), the freeze-out condition $s/T^3\simeq7$ remains valid for $\mu\lesssim 0.3~$GeV. Then, due to the dependence of $T$ on $\mu$, the values of $s/T^3$ increase with increasing $\mu$. In accordance with this observation, we found that the entropy density remains constant with increasing $\mu$. Thus, we conclude that almost no information is going lost through Hawking-Unruh radiation from charged black holes. It is worthwhile to highlight that the freeze-out temperature from charged black holes is determined independent on both freeze-out conditions

Nonextensive statistics and multiplicity distribution in hadronic collisions

The number of particles in a relativistic gas is studied in terms of Tsallis’ nonextensive statistics. For an entropic index q>1 the multiplicity distribution is wider than the Poisson distribution with the same average number of particles, being similar to the negative binomial distribution commonly used in phenomenological analysis of hadron production in high-energy collisions.

Thermal hadron production in high-energy collisions

It is shown that hadron abundances in high-energy , pp and collisions, calculated by assuming that particles originate in hadron-gas fireballs at thermal and partial chemical equilibrium, are in very good agreement with the data. The freeze-out temperature of the hadron-gas fireballs turns out to be nearly constant over a large centre-of-mass energy range and not dependent on the initial colliding system. The only deviation from chemical equilibrium resides in the incomplete strangeness phase-space saturation. Preliminary results of an analysis of hadron abundances in S+S and S+Ag heavy-ion collisions are presented.