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Register a new userSpectral functions of strange vector mesons in asymmetric hyperonic matter
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We study the medium modifications of the spectral functions as well as production cross-sections of the strange vector mesons ($phi$, $K^*$ and $bar {K^*}$) in isospin asymmetric strange hadronic matter. These are obtained from the in-medium masses of the open strange mesons and the decay widths $phi rightarrow Kbar K$, $K^* rightarrow Kpi$ and $bar {K^*} rightarrow {bar K}pi$ in the hadronic medium. The decay widths are computed using a field theoretic model of composite hadrons with quark/antiquark constituents, from the matrix element of the light quark-antiquark pair creation term of the free Dirac Hamiltonian between the initial and final states. The matrix element is multiplied with a coupling strength parameter for the light quark-antiquark pair creation, which is fitted to the observed vacuum decay width of the decay process. There are observed to be substantial modifications of the spectral functions as well as production cross-sections of these vector mesons due to isospin asymmetry as well as strangeness of the hadronic medum at high densities. These studies should have observable consequences, e.g. in the yield of the hidden and open strange mesons arising from the isospin asymmetric high energy heavy ion collisions at the Compressed baryonic matter (CBM) experiments at the future facility at GSI.
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We study the properties of $K$ and $bar K$ mesons in nuclear matter at finite temperature from a chiral unitary approach in coupled channels which incorporates the $s$- and p-waves of the kaon-nucleon interaction. The in-medium solution accounts for Pauli blocking effects, mean-field binding on all the baryons involved, and $pi$ and kaon self-energies. We calculate $K$ and $bar K$ (off-shell) spectral functions and single particle properties. The $bar K$ effective mass gets lowered by about -50 MeV in cold nuclear matter at saturation density and by half this reduction at T=100 MeV. The p-wave contribution to the ${bar K}$ optical potential, due to $Lambda$, $Sigma$ and $Sigma^*$ excitations, becomes significant for momenta larger than 200 MeV/c and reduces the attraction felt by the $bar K$ in the nuclear medium.The $bar K$ spectral function spreads over a wide range of energies, reflecting the melting of the $Lambda (1405)$ resonance and the contribution of $YN^{-1}$ components at finite temperature. In the $KN$ sector, we find that the low-density theorem is a good approximation for the $K$ self-energy close to saturation density due to the absence of resonance-hole excitations. The $K$ potential shows a moderate repulsive behavior, whereas the quasi-particle peak is considerably broadened with increasing density and temperature. We discuss the implications for the decay of the $phi$ meson at SIS/GSI energies as well as in the future FAIR/GSI project.
The medium modifications of the open charm mesons ($D$ and $bar D$) are studied in isospin asymmetric nuclear matter in the presence of strong magnetic fields, using a chiral effective model. The mass modifications of these mesons in the effective hadronic model, arise due to their interactions with the protons, neutrons and the scalar mesons (non-strange isoscalar $sigma$, strange isoscalar, $zeta$ and non-strange isovector, $delta$), in the magnetized nuclear matter. In the presence of magnetic field, for the charged baryon, i.e., the proton, the number density as well as the scalar density have contributions due to the summation over the Landau energy levels. For a given value of the baryon density, $rho_B$, and isospin asymmetry, the scalar fields are solved self consistently from their coupled equations of motion. The modifications of the masses of the $D$ and $bar D$ mesons are calculated, from the medium modifications of the scalar fields and the nucleons. The effects of the anomalous magnetic moments of the nucleons on the masses of the open charm mesons are also investigated in the present work. The effects of isospin asymmetry as well as of the anomalous magnetic moments are observed to be prominent at high densities for large values of magnetic fields.
The masses of the strange mesons ($K$, $K^*$ and $phi$) are investigated in the presence of strong magnetic fields. The changes in the masses of these mesons arise from the mixing of the pseusdoscalar and vector mesons in the presence of a magnetic field. For the charged mesons, these mass modifications are in addition to the contributions from the lowest Landau energy levels to their masses. The decay widths, $phi rightarrow Kbar K$ and $K^* rightarrow Kpi$, in the presence of the magnetic field are studied using a field theoretic model of composite hadrons with constituent quarks/antiquarks. The model uses the free Dirac Hamiltonian in terms of the constituent quark fields as the light quark antiquark pair creation term and explicit constructions for the meson states in terms of the constituent quarks and anitiquarks to study the decay processes. The study of the masses and decay widths of the strange mesons in strong magnetic fields can have observable consequences on the production of the open and hidden strange mesons in the peripheral ultra high energy collisions at LHC, where the created magnetic field can be huge.
We report on a self-consistent calculation of the in-medium spectral functions of the rho and omega mesons at finite baryon density. The corresponding in-medium dilepton spectrum is generated and compared with HADES data. We find that an iterative calculation of the vector meson spectral functions provides a reasonable description of the experimental data.
The in-medium spectral functions of $rho$ and $omega$ mesons and the broadening of the nucleon resonances at finite baryon density are calculated self-consistently by combining a resonance dominance model for the vector meson production with an extended vector meson dominance model. The influence of the in-medium modifications of the vector meson properties on the dilepton spectrum in heavy-ion collisions is investigated. The dilepton spectrum is generated for the C+C reaction at 2.0$A$ GeV and compared with recent HADES Collaboration data. The collision dynamics is then described by the Tubingen relativistic quantum molecular dynamics transport model. We find that an iterative calculation of the vector meson spectral functions that takes into account the broadening of the nucleon resonances due to their increased in-medium decay branchings is convergent and provides a reasonable description of the experimental data in the mass region $0.45leq M leq 0.75$ GeV. On the other side, the theoretical calculations slightly underestimate the region $m_pileq M leq 0.4$ GeV. Popular in-medium scenarios such as a schematic collisional broadening and dropping vector mesons masses are discussed as well.
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