Strange pentaquark hadrons in statistical hadronization

Abstract

We study, within the statistical hadronization model, the influence of narrow strangeness carrying baryon resonances (pentaquarks) on the understanding of particle production in relativistic heavy ion collisions. There is a great variation of expected yields as function of heavy ion collision energy due to rapidly evolving chemical conditions at particle chemical freeze-out. At relatively low collision energies, these new states lead to improvement of statistical hadronization fits.PACS numbers: 24.10. Pa,13.60.Rj,12.38.Mh Enhanced production of strange hadrons in relativistic heavy ion collisions is well established [1,2]. The availability of a high abundance of strangeness favors production of strange hadron resonances, a topic of current intense experimental interest in the field of relativistic heavy ion collisions [3,4,5,6,7,8,9]. The discovery by the NA49 collaboration [10]of a new Ξ −− (1862) I = 3/2 narrow Γ < 5 MeV resonance in their pp background, rather than in the AA foreground data at projectile energy 158 GeV ( √ s NN = 17.2 GeV) poses the question in which conditions one should look in heavy ion collisions for such new resonances. This newly discovered hadron resonance has, given the mass and charge, an exceedingly narrow width. This feature is common with Θ + (1540), another recently reported resonance [11,12,13,14], which decays into the channel with quark content uudds and I = 0. This is believed to be the predicted [15], lowest mass, pentaquark state [16]. The Ξ * (1862) can be interpreted as its most massive isospin quartet member ssddū, ssudū, ssudd, ssuud with electrical charge varying, respectively, from −2 to +1, in units of |e|.Appearance of these new resonances can have many consequences in the field of heavy ion collisions. We at first explore how the introduction into the family of hadronic particles of these two new resonances, Θ + (1540) and Ξ * (1862), influence the results of statistical hadronization fit to relativistic heavy ion hadron production experimental results. We use the same data set as has been employed in Ref [2,17,18] and obtain predictions of how the relative abundances of these new resonant states vary as function of the heavy ion collision energy.Importantly, only the two already identified states with I = 0, and I = 3/2 of the anti decuplet, which also includes the I = 1/2, and I = 1 states are of relevance in the study of the statistical hadronization fits. Thus, in our analysis, we do not depend on the unknown masses of I = 1/2, and I = 1 states. However, the interpretation of the newly discovered narrow states as pentaquarks enters our considerations decisively. The pentaquark valance quark content enters the assigned chemical fugacities and phase space occupancies. The yield is proportional to the presumed spin degeneracy of the new states, taken to be two for a spin 1/2 anti decuplet.In our approach [2,17,18], as in other recent work [19], the chemical equilibrium and non-equilibrium is considered. Accordingly, we allow quark pair phase space occupancies,...

Exotic hadrons in heavy ion collisions

“…On the other hand, the recent LEPS result maintains a positive signal [82]. The most suitable hadronic decay mode for its identification in an inclusive experiment is Θ + → K 0 p. The production rate in heavy ion collisions has been estimated in the statistical model [83][84][85] and in the coalescence model [17]. In the quark model, the spin-parity of Θ + is 1/2 − if all five quarks are in the s-wave orbit but is 1/2 + after including the strong diquark correlation [86].…”

Hadron production and phase changes in relativistic heavy-ion collisions

“…We thus present in table 5 predictions for the production rates of Θ + and Ξ −− . These yields are highly sensitive to the hadronization conditions [74], and were obtained using the parameters of the fits here presented.…”

Self-consistent quasiparticle model for quark-gluon plasma

“…Many attempts in this line were not completely successful [7,8,9]. Therefore, several phenomenological models with two or more fitting parameters, like confinement models [10], strongly coupled plasma (SCQGP) [11], strongly interacting plasma (sQGP) [12], qQGP [1,2,3,4,5], liquid model [13] and so on, were proposed. By adjusting parameters of the model one may fit the LGT results.…”