Chiral theory of mesons in dense baryonic matter (I)

International Journal of Modern Physics A, 2003

We present an analytical description of the phase transitions from a nucleon gas to nuclear matter and from nuclear matter to quark matter within the same model. The equation of state for quark and nuclear matter is encoded in the effective potential of a linear sigma model. We exploit an exact differential equation for its dependence upon the chemical potential $\mu$ associated to conserved baryon number. An approximate solution for vanishing temperature is used to discuss possible phase transitions as the baryon density increases. For a nucleon gas and nuclear matter we find a substantial density enhancement as compared to quark models which neglect the confinement to baryons. The results point out that the latter models are not suitable to discuss the phase diagram at low temperature.

1999

E. Oset, A. Hosaka, J.C. Nacher, M. Oka, J.A. Oller, A. Parreño, J.R. Peláez, A. Ramos , H. Toki Departamento de F́ısica Teórica and IFIC, Valencia, Spain Numazu College of Technology, Numazu, Japan Tokyo Institute of Technology, Tokyo, Japan Institute for Nuclear Theory, Washington, Seattle, USA Departamento de F́ısica Teórica, Madrid, Spain Departament d’Estructura i Constituents de la Matèria, Barcelona, Spain Research Center for Nuclear Physics (RCNP), Osaka, Japan

Nuclear Physics A, 2000

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and K − atoms.

2004

We point out that the spectrum of pseudoscalar and scalar mesons exhibits a cuasi-degenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum. Based on the empirical linear rising of the mass of a hadron with the number of constituent quarks which yields a mass around 1.4 GeV for tetraquarks, we conjecture that this cuasi-chiral nonet arises from the mixing of a chiral nonet composed of tetraquarks with conventional qq states. We explore this possibility in the framework of a chiral model assuming a tetraquark chiral nonet around 1.4 GeV with chiral symmetry realized directly. We stress that UA(1) transformations can distinguish qq from tetraquark states, although it cannot distinguish specific dynamics in the later case. We find that the measured spectrum is consistent with this picture. In general, pseudoscalar states arise as mainly qq states but scalar states turn out to be strong admixtures of qq and tetraquark states. We work out also the model predictions for the most relevant couplings and calculate explicitly the strong decays of the a0(1450) and K * 0 (1430) mesons. From the comparison of some of the predicted couplings with the experimental ones we conclude that observable for the isovector and isospinor sectors are consistently described within the model. The proper description of couplings in the isoscalar sectors would require the introduction of glueball fields which is an important missing piece in the present model.

Physical Review D, 2004

We point out that the spectrum of pseudoscalar and scalar mesons exhibits a cuasi-degenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum. Based on the empirical linear rising of the mass of a hadron with the number of constituent quarks which yields a mass around 1.4 GeV for tetraquarks, we conjecture that this cuasi-chiral nonet arises from the mixing of a chiral nonet composed of tetraquarks with conventional qq states. We explore this possibility in the framework of a chiral model assuming a tetraquark chiral nonet around 1.4 GeV with chiral symmetry realized directly. We stress that UA(1) transformations can distinguish qq from tetraquark states, although it cannot distinguish specific dynamics in the later case. We find that the measured spectrum is consistent with this picture. In general, pseudoscalar states arise as mainly qq states but scalar states turn out to be strong admixtures of qq and tetraquark states. We work out also the model predictions for the most relevant couplings and calculate explicitly the strong decays of the a0(1450) and K * 0 (1430) mesons. From the comparison of some of the predicted couplings with the experimental ones we conclude that observable for the isovector and isospinor sectors are consistently described within the model. The proper description of couplings in the isoscalar sectors would require the introduction of glueball fields which is an important missing piece in the present model.

Physical Review C, 2011

The chiral model is used to describe quark matter under strong magnetic fields and compared to other models, the MIT bag model and the two flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic field vacuum corrections are not taken into account explicitly the parameters of the models should be fitted to low density meson properties in the presence of the magnetic field.

Physical Review D, 2008

We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p 4) in the two-and tree-flavor picture. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of baryon chiral perturbation theory (ChPT) allows to deduce a connection between our parameters and those of baryon ChPT.

Journal of Mathematical Sciences, 2000

We compare two QCD-inspired quark models with four-fermion interaction, without and with the remnant coupling to low-energy gluons, in the regime of dynamical chiral symmetry breaking (DCSB). The first one, the Nambu-Jona-Lasinio (NJL) model ensures the factorization of scalar and pseudoscalar meson poles in correlators, the well-known Nambu relation between the scalar meson mass and the dynamical quark mass, m σ = 2m dyn , and the residual chiral symmetry in coupling constants characteristic for the linear σ-model. The second one, the Gauged NJL model, happens to be qualitatively different from the NJL model, namely, the Nambu relation is not valid and the factorization of light meson poles does not entail the residual chiral symmetry, i.e. it does not result in a linear σ-model. The more complicated DCSB pattern in the GNJL model is fully explained in terms of excited meson states with the same quantum numbers. The asymptotic restrictions on parameters of scalar and pseudoscalar meson states are derived from the requirement of chiral symmetry restoration at high energies.

2010

We review recent results on properties of the meson gas relevant for Heavy Ion Collision and Nuclear Matter experiments, within the framework of chiral lagrangians. In particular, we describe the temperature and density evolution of the σ and ρ poles and its connection with chiral symmetry restoration, as well as the chemical nonequilibrated phase and transport coefficients.

Physical Review D, 1992

We report on recent advances in the understanding of hadrons containing one heavy quark, providing a general introduction to the main ideas behind the heavy quark symmetry. We concentrate on the synthesis of heavy quark and chiral symmetries, describing recent calculations of heavy meson and baryon decays through processes involving strong, electromagnetic and semileptonic weak interactions.