Last Call for RHIC Predictions
This paper contains the individual contributions of all speakers of the session on 'Last Call for RHIC Predictions' at Quark Matter 99, and a summary by the convenor.
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arXiv subjects
J. Schaffner-Bielich
Publications and source records attributed to J. Schaffner-Bielich.
Chiral model for dense, hot and strange hadronic matter
An extended chiral SU(3) model is applied to the description of dense, hot and strange hadronic matter. The degrees of freedom are the baryon octet and decuplet and the spin-0 and spin-1 meson multiplets. The parameters of the model are fitted to the hadron masses in vacumm, infinite nuclear matter properties and soft pion theorems. At high densities the appearance of density isomers cannot be ruled out and extrapolation to finite temperature exhibits a first order phase transition at $T \approx 150 MeV$. The predicted dropping baryon masses lead to drastically changed particle ratios compared to ideal gas calculations.
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DCC dynamics with the SU(3) linear sigma model
The SU(3) extension of the linear sigma model is employed to elucidate the effect of including strangeness on the formation of disoriented chiral condensates. By means of a Hartree factorization, approximate dispersion relations for the 18 scalar and pseudoscalar meson species are derived and their self-consistent solution makes it possible to trace out the thermal path of the two order parameters as well as delineate the region of instability within which spontaneous pair creation becomes possible. The results depend significantly on the employed sigma mass, with the highest values yielding the largest regions of instability. An approximate solution of the equations of motion for the order parameter in scenarios emulating uniform scaling expansions show that even with a rapid quench only the pionic modes grow unstable. Nevertheless, the rapid and oscillatory relaxation of the order parameters leads to enhanced production of both pions and (to a lesser degree) kaons.
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Neutron stars and quark phases in the NJL model
We study the possible existence of deconfined quark matter in the interior of neutron stars using the Nambu-Jona-Lasinio model to describe the quark phase. We find that typical neutron stars with masses around 1.4 solar masses do not possess any deconfined quark matter in their center. This can be traced back to the property of the NJL model which suggests a large constituent strange quark mass over a wide range of densities.
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Nuclei in a chiral SU(3) model
Nuclei can be described satisfactorily in a nonlinear chiral SU(3)-framework, even with standard potentials of the linear $σ$-model. The condensate value of the strange scalar meson is found to be important for the properties of nuclei even without adding hyperons. By neglecting terms which couple the strange to the nonstrange condensate one can reduce the model to a Walecka model structure embedded in SU(3). We discuss inherent problems with chiral SU(3) models regarding hyperon optical potentials.
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Charmlets
We discuss the possibility, that multiply charmed exotics are produced in ultrarelativistic heavy ion collisions. Production probabilities at RHIC are estimated and found to be large enough to allow for the possible detection of single and double charmed exotics. We demonstrate that charm matter is bound due to an attractive one-gluon exchange potential. Furthermore, we study the color magnetic and color electric potential separately, as well as the group structure of such exotics and estimate their masses.
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Chiral Lagrangian for strange hadronic matter
A generalized Lagrangian for the description of hadronic matter based on the linear $SU(3)_L \times SU(3)_R$ $σ$-model is proposed. Besides the baryon octet, the spin-0 and spin-1 nonets, a gluon condensate associated with broken scale invariance is incorporated. The observed values for the vacuum masses of the baryons and mesons are reproduced. In mean-field approximation, vector and scalar interactions yield a saturating nuclear equation of state. We discuss the difficulties and possibilities to construct a chiral invariant baryon-meson interaction that leads to a realistic equation of state. It is found that a coupling of the strange condensate to nucleons is needed to describe the hyperon potentials correctly. The effective baryon masses and the appearance of an abnormal phase of nearly massless nucleons at high densities are examined. A nonlinear realization of chiral symmetry is considered, to retain a Yukawa-type baryon-meson interaction and to establish a connection to the Walecka-model.
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