20 research outputs found
Resonance states below pion-nucleon threshold and their consequences for nuclear systems
Regular sequences of narrow peaks have been observed in the missing mass
spectra in the reactions pp --> p pi^+ X and pd --> ppX_1 below pion-production
threshold. They are interpreted in the literature as manifestations of
supernarrow light dibaryons, or nucleon resonances, or light pions forming
resonance states with the nucleon in its ground state. We discuss how existence
of such exotic states would affect properties of nuclear systems. We show that
the neutron star structure is drastically changed in all three cases. We find
that in the presence of dibaryons or nucleon resonances the maximal possible
mass of a neutron star would be smaller than the observational limit. Presence
of light pions does not contradict the observed neutron star masses. Light
pions allow for the existence of extended nuclear objects of arbitrary size,
bound by strong and electromagnetic forces.Comment: preprint ECT*-02-18, 6 pages, 3 figure
Phi Mesons from a Hadronic Fireball
Production of mesons is considered in the course of heavy-ion
collisions at SPS energies. We investigate the possible difference in momentum
distributions of mesons measured via their leptonic () and
hadronic () decays. Rescattering of secondary kaons in the dense hadron
gas together with the influence of in-medium kaon potential can lead to a
relative decrease of a yield observed in the hadronic channel. We
analyze how the in-medium modifications of meson properties affect apparent -
reconstructed momentum distributions of mesons. Quantitative results are
presented for central Pb+Pb collisions at .Comment: style Revtex4,9 pages, 5 figures. submitted to Phys. Rev.
Negative Kaons in Dense Baryonic Matter
Kaon polarization operator in dense baryonic matter of arbitrary isotopic
composition is calculated including s- and p-wave kaon-baryon interactions. The
regular part of the polarization operator is extracted from the realistic
kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions
of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly
into account in the pole and regular terms with inclusion of mean-field
potentials. The baryon-baryon correlations are incorporated and fluctuation
contributions are estimated. Results are applied for K- in neutron star matter.
Within our model a second-order phase transition to the s-wave K- condensate
state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are
included. We show that the second-order phase transition to the p-wave
condensate state may occur at densities in
dependence on the parameter choice. We demonstrate that a first-order phase
transition to a proton-enriched (approximately isospin-symmetric) nucleon
matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2
\rho_0. The transition is accompanied by the suppression of hyperon
concentrations.Comment: 41 pages, 24 figures, revtex4 styl