Strangeness, equilibration, hadronization

Abstract

Abstract. In these remarks I explain the motivation which leads us to consider chemical nonequilibrium processes in flavor equilibration and in statistical hadroniziation of quark-gluon plasma (QGP). Statistical hadronization allowing for chemical non-equilibrium is introduced. The reesults of fits to RHIC-130 results, including multistrange hadrons, are shown to agree only with the model of an exploding QGP fireball. Historical backgroundThe topic we discuss today, production of hadrons in statistical hadronization in high energy heavy ion collisions, has been the subject of several diploma and doctor thesis at the University Frankfurt in late 70's and early 80's. At the time, in a field void of any experimental result, I competed with a Hungarian hadrochemistry group lead by the chair of this discussion session, Prof. J. Zimanyi.We both passed through natural evolution stages. We were at first considering the equilibrium particle abundances expected to arise when Mr. EquilibriX holds in his hand hot and dense hadron matter fireball, which evaporated these particles. This work was followed by the development of kinetic theory of strangeness production, which was precipitated by the finding of the Budapest group, that light quark interactions were not fast enough to produce strangeness abundantly.We learned to appreciate that the yields of newly produced quarks were not necessarily given by the chemical equilibrium statistical model. The physics reason which lead us to explore the kinetic theory was relatively short available reaction time in relativistic heavy ion collisions, in general not allowing for the achievement of an equilibrium particle abundance. These remarks apply to the case that the dense matter fireball is made of hadrons, or deconfined quarks. Our work was extended to compare these two so different matter phases.This kinetic theory work has inspired the chemical non-equilibrium study of hadronization of quark-gluon plasma (QGP), and we were able to show that in a sudden hadronization process specific properties of QGP will be imparted in hadronization on particle yields. All these developments were then summarized in a relatively widely known theoretical review [1].When the first multistrange hadron experimental results arrived 10 years ago, the analysis applied introduced the chemical non-equilibrium [2], which then was generally accepted as being an important element of data analysis. This analysis addressed solely

Non-equilibrium Hadrochemistry in QGP Hadronization

“…in the letter case we fix the chemical parameters to their equilibrium value. We observe a considerable improvement in the statistical significance of the results of chemical non-equilibrium fits (see bottom line), as we have seen in our related earlier RHIC work [43,44], in consistency with the situation at SPS. Next to the fitted results, we show in parenthesis the contribution to the error (χ 2 ) for each entry.…”

“…Our current results, when compared to our earlier effort [43,44] show a 7% reduction in the freeze-out temperature both for equilibrium and non-equilibrium case. Such lower T reduces selectively the relative yield of baryons.…”

Strangeness and the Discovery of Quark-Gluon Plasma

“…This effect was predicted and originates in an increasing lifespan of the fireball [17]. The over-saturation of the phase space has been also expected due to both, the dynamics of expansion [18], and/or reduction in phase space size as a parton based matter turns into HG [19]. This latter effect is also held responsible for the saturation of light quark phase space γ q → e mπ /2T .…”

Schematic model for QCD. II. Finite temperature regime

“…Considering the simplicity of the model it is surprising that the absolute production rate is well reproduced. This feature is common to other thermodynamical descriptions of the transition from the QGP to the hadron-gas [23,21].…”