Окремi фiзичнi фрiзаути дивних та недивних адронiв та проблема залишкової хiмiчної нерiвноваги дивностi в релятивiстських зiткненнях важких iонiв

• Main Authors: Bugaev, K. A., Oliinychenko, D. R., Sagun, V. V., Ivanytskyi, A. I., Cleymans, J., Mironchuk, E. S., Nikonov, E. G., Taranenko, A. V., Zinovjev, G. M.
• Format: Article
• Language: English
• Published: Publishing house "Academperiodika" 2019
• Subjects: chemical freeze-out; strangeness enhancement/suppression factor ys; Strangeness Horn; hadron multiplicities; -
• Online Access: https://ujp.bitp.kiev.ua/index.php/ujp/article/view/2019044

We present an elaborate version of the hadron resonance gas model with the combined treatment of separate chemical freeze-outs for strange and non-strange hadrons and with an additional ys factor which accounts for the remaining strange particle non-equilibration. Within the suggested approach, the parameters of two chemical freeze-outs are connected by the conservation laws of entropy, baryonic charge, third isospin projection, and strangeness. The developed model enables us to perform a high-quality fit of the hadron multiplicity ratios measured at AGS, SPS, and RHIC with X2/dof ≃ 0.93. A special attention is paid to a successful description of the Strangeness Horn. The well-known problem of selective suppression of Λ and Ξ hyperons is also discussed. The main result is that, for all collision energies, the ys factor is about 1 within the error bars, except for the center-of-mass collision energy 7.6 GeV, at which we find about 20% enhancement of strangeness. Also we confirm the existence of strong jumps in the pressure, temperature, and effective number of degrees of freedom at the stage of strange particle chemical freeze-out, when the center-of-mass collision energy changes from 4.3 to 4.9 GeV. We argue that these irregularities may signal about the quark-hadron phase transition.