Mass shift, width broadening and spectral density of rho-mesons produced in heavy ion collisions

Our recent work on modifications of rho-mesons formed at the last stage of evolution of hadronic matter produced in heavy ion collisions is summarized. It is found that while the mass shift is on the order of a few tens of MeV, the width and spectral density become so broad that rho may lose its identity as a well defined resonance.Comment: Talk given at Quark Matter '99, the 14th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Torino, Italy, May 10-14, 1999. 4 pages, Latex, 4 PS figure

Formation of light antinuclei and "dense gas" stage in heavy ion collisions

The antideuteron and antihelium-3 production rates at high-energy heavy ion collisions are calculated in the framework of fusion mechanism when participating particles are moving in the mean field of other fireball constituents. It is shown that coalescence parameters can be found from the requirement of balance between created and disintegrated antinuclei. The explicit formulae for coalescence parameters are presented and compared with experimental data.Comment: To be published in "Proceedings of the 18th International Nuclear Physics Divisional Conference of the EPS (NPDC18), 2004.

Chiral Symmetry Restoration and Parity Mixing

We derive the expressions of the vector and axial current from a chiral Lagrangian restricted to nucleons and pions. They display mixing terms between the axial and vector currents. We study the modifications in the nuclear medium of the coupling constants of the axial current, namely the pion decay constant and the nucleonic axial one due to the requirements of chiral symmetry. We express the renormalizations in terms of the local scalar pion density. The latter also governs the quark condensate evolu- tion and we discuss the link between this evolution and the renormaliza- tions. In the case of the nucleon axial coupling constant this renormali- zation corresponds to a new type of exchange currents, with two exchanged pions. We give an estimate for the resulting quenching. Although moderate it helps explaining the quenching experimentally observed.Comment: Latex, 15 pages. Several references and one figure added. New discussion of some points has been included. Treatment of the renormali- zation of the nucleon axial coupling constant has been develope

The Goldberger -- Treiman Relation, gAg_A and gπNNg_{\pi NN} at T≠0T\neq 0

The Goldberger-Treiman relation is shown to persist in the chiral limit at finite temperatures to order $O(T^2)$. The $T$ dependence of $g_A$ turns out to be the same as for $F_{\pi}$, $g_{A}(T)=g_{A}(0)(1-T^2/12F^2)$, while $g_{\pi NN}$ is temperature independent to this order. The baryon octet ${\cal D}$ and ${\cal F}$ couplings also behave as $F_{\pi}$ if only pions are massless in the pseudoscalar meson octet.Comment: 7p, NSF-ITP-93-145, BUTP-93/27, PUTP-1433, November 199

Next-to-leading-order temperature corrections to correlators in QCD

Corrections of order $T^4$ to vector and axial current correlators in QCD at a finite temperature $T<T_c$ are obtained using dispersion relations for the amplitudes of deep inelastic scattering on pions. Their relation with the operator product expansion is presented. An interpretation of the results in terms of $T$-dependent meson masses is given: masses of $\rho$ and $a_1$ start to move with temperature in order $T^4$.Comment: 13 pages, no figures, CERN-TH.7215/94, BUTP-94/

Lattice-QCD based Schwinger-Dyson approach for Chiral Phase Transition

Dynamical chiral-symmetry breaking in QCD is studied with the Schwinger-Dyson (SD) formalism based on lattice QCD data, i.e., LQCD-based SD formalism. We extract the SD kernel function $K(p^2)$ in an Ansatz-independent manner from the lattice data of the quark propagator in the Landau gauge. As remarkable features, we find infrared vanishing and intermediate enhancement of the SD kernel function $K(p^2)$. We apply the LQCD-based SD equation to thermal QCD with the quark chemical potential $\mu_q$. We find chiral symmetry restoration at $T_c \simeq 100{\rm MeV}$ for $\mu_q=0$. The real part of the quark mass function decreases as $T$ and $\mu_q$. At finite density, there appears the imaginary part of the quark mass function, which would lead to the width broadening of hadrons.Comment: 4 pages, 4 figures, Presented at Workshop on QCD Down Under, Barossa Valley and Adelaide, Australia, 10-19 Mar 200