Probing the strange quark condensate by di-electrons from phi meson decays in heavy-ion collisions at SIS energies

QCD sum rules predict that the change of the strange quark condensate $<\bar s s>$ in hadron matter at finite baryon density causes a shift of the peak position of the di-electron spectra from $\phi$ meson decays. Due to the expansion of hadron matter in heavy-ion collisions, the $\phi$ peak suffers a smearing governed by the interval of density in the expanding fireball, which appears as effective broadening of the di-electron spectrum in the $\phi$ region. The emerging broadening is sensitive to the in-medium change of $<\bar s s>$. This allows to probe directly in-medium modifications of $$ via di-electron spectra in heavy-ion collisions at SIS energies with HADES

Evaluation of QCD sum rules for light vector mesons at finite density and temperature

QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters for the lightest vector mesons $\rho$, $\omega$ and $\phi$ in a strongly interacting medium. For conditions relevant for the starting experiments at HADES we find that the in-medium mass shifts of the $\rho$ and $\omega$ mesons are governed, within the Borel QCD sum rule approach, by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the density dependence of the four-quark condensate reflects directly the decreasing mass of the $\rho$ meson and can lead to a change of the sign of the $\omega$ meson mass shift as a function of the density. In contrast, the in-medium mass of the $\phi$ meson is directly related to the chiral strange quark condensate which seems correspondingly accessible

Impact of Four-Quark Condensates on In-Medium Effects of Hadrons

Spectral properties of hadrons in nuclear matter are treated in the framework of QCD sum rules. The influence of the ambient strongly interacting medium is encoded in various condensates. Especially, the structure of different four-quark condensates and their density dependencies in light quark systems are exemplified for the omega meson and the nucleon.Comment: Contribution to Quark Confinement and the Hadron Spectrum VII, 02.-07.09.2006, Ponta Delgada, Portuga

Centrality dependence of thermal parameters in heavy-ion collisions at SPS and RHIC

We analyze the centrality dependence of thermal parameters describing hadron multiplicities, hadron spectra and dilepton spectra in heavy-ion collisions at SPS and RHIC energies.Comment: contribution to the Int. Workshop XXX on Gross Properties of Nuclei and Nuclear Excitations: Ultrarelativistic Heavy-Ion Collisions, Hirschegg, Jan. 13 - 19, 200

Electromagnetic Probes of Strongly Interacting Matter: Probes of Chiral Symmetry Restoration?

The QCD sum rule approach to in-medium modifications of the omega meson in nuclear matter is reviewed with emphasis of its relation to 4-quark condensates and chiral symmetry restoration. Possible implications of the CB-TAPS experiment for the reaction gamma A -> A' omega (-> pi0 gamma) are sketched and the particularly important role of di-electron probes, accessible with HADES, is highlighted. A brief update of a parametrization of the previous dilepton and photon probes from CERES and WA98 of heavy-ion collisions at CERN-SPS energies is presented.Comment: Contribution to Workshop on In-Medium Hadron Physics, Giessen, Nov. 11-13; 11 page

Strangeness Saturation: Dependence on System-Size, Centrality and Energy

The dependence of the strangeness saturation factor on the system size, centrality and energy is studied in relativistic heavy-ion collisions.Comment: contribution for Proc. 19th Winter Workshop on Nuclear Dynamics, Breckenridge, February 8-15, 200

Exclusive charge exchange reaction pD->n(pp) within the Bethe-Salpeter formalism

The exclusive charge exchange reaction pD->n(pp) at intermediate and high energies is studied within the Bethe-Salpeter formalism. The final state interaction in the detected pp pair at nearly zero excitation energy is described by the 1S0 component of the Bethe-Salpeter amplitude. Results of numerical calculations of polarization observables and differential cross-section persuade that, as in the non-relativistic case, this reaction (i) can be utilized as a ``relativistic deuteron polarimeter'' and (ii) delivers further information about the elementary nucleon-nucleon charge-exchange amplitude.Comment: 38 pages, 10 eps-figure