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We discuss the possibility of producing a new kind of nuclear system by putting a few antibaryons inside ordinary nuclei. The structure of such systems is calculated within the relativistic mean field model assuming that the nucleon and antinucleon potentials are related by the G parity transformation. The presence of antinucleons leads to decreasing vector potential and increasing scalar potential for the nucleons. As a result, a strongly bound system of high density is formed. Due to the significant reduction of the available phase space the annihilation probability might be strongly suppressed in such systems.
The high E(T) drop of J / psi to Drell-Yan ratio from the statistical c anti-c coalescence model
(2002)
The dependence of the J/psi yield on the transverse energy ET in heavy ion collisions is considered within the statistical c¯c coalescence model. The model fits the NA50 data for Pb+Pb collisions at the CERN SPS even in the high-ET region (ET >< 100 GeV). Here ET -fluctuations and ET -losses in the dimuon event sample naturally create the celebrated drop in the J/psi to Drell-Yan ratio.
Production of J/ψ mesons in heavy ion collisions is considered within the statistical coalescence model. The model is in agreement with the experimental data of the NA50 Collaboration for Pb+Pb collisions at 158 AGeV in a wide centrality range, including the so-called “anomalous” suppression domain. The model description of the J/ψ data requires, however, strong enhancement of the open charm production in central Pb+Pb collisions. This model prediction may be checked in the future SPS runs.
The recently published experimental dependence of the J/psi suppression pattern in Pb+Pb collisions at the CERN SPS on the energy of zero degree calorimeter EZDC are analyzed. It is found that the data obtained within the minimum bias analysis (using theoretical Drell-Yan ) are at variance with the previously published experimental dependence of the same quantity on the transversal energy of neutral hadrons ET . The discrepancy is related to the moderate centrality region: 100 << Np << 200 (Np is the number of nucleon participants). This could result from systematic experimental errors in the minimum bias sample. A possible source of the errors may be contamination of the minimum bias sample by o -target interactions. The data obtained within the standard analysis (using measured Drell-Yan multiplicity) are found to be much less sensitive to the contamination.
We study the bound states of anti-nucleons emerging from the lower continuum in finite nuclei within the relativistic Hartree approach including the contributions of the Dirac sea to the source terms of the meson fields. The Dirac equation is reduced to two Schr¨odinger-equivalent equations for the nucleon and the anti-nucleon respectively. These two equations are solved simultaneously in an iteration procedure. Numerical results show that the bound levels of anti-nucleons vary drastically when the vacuum contributions are taken into account. PACS number(s): 21.10.-k; 21.60.-n; 03.65.Pm
The in-medium properties of the vector mesons are known to be modified significantly in hot and dense hadronic matter due to vacuum polarisation e ects from the baryon sector in the Walecka model. The vector meson mass drops significantly in the medium due to the e ects of the Dirac sea. In the variational approach adopted in the present paper, these e ects are taken into account through a realignment of the ground state with baryon condensates. Such a realignment of the ground state becomes equivalent to summing of the baryonic tadpole diagrams in the relativistic Hartree approximation (RHA). The approximation scheme adopted here goes beyond RHA to include quantum e ects from the scalar meson and is nonperturbative and self consistent. It includes multiloop e ects, thus corresponding to a di erent approximation as compared to the one loop approximation of including scalar field quantum corrections. In the present work, we study the properties of the vector mesons in the hot and dense matter as modified due to such quantum correction e ects from the baryon as well as scalar meson sectors. These medium modifications of the properties of the vector mesons are reflected, through the shifting and broadening of the respective peaks, in the low mass dilepton spectra. There is broadening of the peaks due to corrections from scalar meson quantum e ects as compared to the relativistic Hartree approximation. It is seen to be rather prominent for the ! meson in the invariant mass plot. PACS number: 21.65.+f,12.40.Yx
We study properties of compact stars with the deconfinement phase transition in their interiors. The equation of state of cold baryon-rich matter is constructed by combining a relativistic mean-field model for the hadronic phase and the MIT Bag model for the deconfined phase. In a narrow parameter range two sequences of compact stars (twin stars), which differ by the size of the quark core, have been found. We demonstrate the possibility of a rapid transition between the twin stars with the energy release of about 10 ^52 ergs. This transition should be accompanied by the prompt neutrino burst and the delayed gamma-ray burst.
We compare different models for hadronic and quark phases of cold baryon rich matter in an attempt to find a deconfinement phase transition between them. For the hadronic phase we consider Walecka type mean field models which describe well the nuclear saturation properties. We also use the variational chain model which takes into account correlation effects. For the quark phase we consider the MIT bag model, the Nambu Jona-Lasinio and the massive quasiparticle models. By comparing pressure as a function of baryon chemical potential we find that crossings of hadronic and quark branches are possible only in some exceptional cases while for most realistic parameter sets these branches do not cross at all. Moreover, the chiral phase transition, often discussed within the framework of QCD motivated models, lies in the region where the quark phases are unstable with respect to the hadronic phase. We discuss possible physical consequences of these findings.
Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R ~ 8 km. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.Jd