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Ukr. J. Phys. 2015, Vol. 59, N 11, p.1043-1050
doi:10.15407/ujpe59.11.1043    Paper

Sagun V.V.1, Oliinychenko D.R.1,2, Bugaev K.A.1, Cleymans J.3, Ivanytskyi A.I.1, Mishustin I.N.2,4, Nikonov E.G.5

1 Bogolyubov Institute for Theoretical Physics, Nat. Acad. of Sci. of Ukraine
(14b, Metrolohichna Str., Kyiv 03680, Ukraine;
e-mail: v_sagun@ukr.net, bugaev@th.physik.uni-frankfurt.de, a_iv_@ukr.net )
2 FIAS,Goethe-University
(1, Ruth-Moufang Str., Frankfurt am Main 60438, Germany;
e-mail: dimafopf@gmail.com, mishustin@fias.uni-frankfurt.de)
3 Department of Physics, University of Cape Town
(Rondebosch 7701, South Africa; e-mail: jean.cleymans@uct.ac.za)
4 Kurchatov Institute, Russian Research Center
(Kurchatov Sqr., Moscow 123182, Russia)
5 Laboratory for Information Technologies, JINR
(Dubna 141980, Russia; e-mail: e.nikonov@jinr.ru)

Strangeness Enhancement at the Hadronic Chemical Freeze-Out

Section: Fields and elementary particles
Original Author's Text: English

Abstract: The chemical freeze-out of hadrons created in the high energy nuclear collisions is studied within a realistic version of the hadron resonance gas model. The chemical non-equilibrium of strange particles is accounted via the usual γs factor, which gives us an opportunity to perform a high quality fit with χ2 /dof ≃ 63.5/55 ≃ 1.15 of the hadronic multiplicity ratios measured from the low AGS to the highest RHIC energies. In contrast to the previous findings, we observe the strangeness enhancement at low energies instead of a suppression. In addition, the performed γs fit allows us to achieve the highest quality of the Strangeness Horn description with χ2 /dof = 3.3/14. For the first time, the top point of the Strangeness Horn is perfectly reproduced, which makes our theoretical horn as sharp as an experimental one. However, the γs fit approach does not sizably improve the description of the multistrange baryons and antibaryons. Therefore, an apparent deviation of the multistrange baryons and antibaryons from the chemical equilibrium requires a further explanation.

Key words: chemical freeze-out, γs factor, Strangeness Horn, hadron multiplicities.