Probing resonance matter with virtual photons

In the energy domain of 1-2 GeV per nucleon, HADES has measured rare penetrating probes (e+e-) in C+C, Ar+KCl, d+p, p+p and p+Nb collisions. For the first time the electron pairs were reconstructed from quasi-free n+p sub-reactions by detecting the proton spectator from the deuteron breakup. An experimentally constrained NN reference spectrum was established. Our results demonstrate that the gross features of di-electron spectra in C+C collisions can be explained as a superposition of independent NN collisions. On the other hand, a direct comparison of the NN reference spectrum with the e+e- invariant mass distribution measured in the heavier system Ar+KCl at 1.76 GeV/u shows an excess yield above the reference, which we attribute to radiation from resonance matter. Moreover, the combined measurement of di-electrons and strangeness in Ar+KCl collisions has provided further intriguing results which are also discussed.Comment: 10 pages, 3 figures, proceedings of the International Nuclear Physics Conference - INPC 2010, Vancouver, Canada, July 4 - 9 201

The algebraic hyperstructure of elementary particles in physical theory

Algebraic hyperstructures represent a natural extension of classical algebraic structures. In a classical algebraic structure, the composition of two elements is an element, while in an algebraic hyperstructure, the composition of two elements is a set. Algebraic hyperstructure theory has a multiplicity of applications to other disciplines. The main purpose of this paper is to provide examples of hyperstructures associated with elementary particles in physical theory.Comment: 13 page

Hadron properties in the nuclear medium

The QCD vacuum shows the dynamical breaking of chiral symmetry. In the hot/dense QCD medium, the chiral order parameter such as $$ is expected to change as function of temperature $T$ and density $\rho$ of the medium, and its experimental detection is one of the main challenges in modern hadron physics. In this article, we discuss theoretical expectations for the in-medium hadron spectra associated with partial restoration of chiral symmetry and the current status of experiments with an emphasis on the measurements of properties of mesons produced in near-ground-state nuclei.Comment: 40 pages, submitted to Reviews of Modern Physic

Pluto: A Monte Carlo Simulation Tool for Hadronic Physics

Pluto is a Monte-Carlo event generator designed for hadronic interactions from Pion production threshold to intermediate energies of a few GeV per nucleon, as well as for studies of heavy ion reactions. This report gives an overview of the design of the package, the included models and the user interface.Comment: XI International Workshop on Advanced Computing and Analysis Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland

Design of the Pluto Event Generator

We present the design of the simulation package Pluto, aimed at the study of hadronic interactions at SIS and FAIR energies. Its main mission is to offer a modular framework with an object-oriented structure, thereby making additions such as new particles, decays of resonances, new models up to modules for entire changes easily applicable. Overall consistency is ensured by a plugin- and distribution manager. Particular features are the support of a modular structure for physics process descriptions, and the possibility to access the particle stream for on-line modifications. Additional configuration and self-made classes can be attached by the user without re-compiling the package, which makes Pluto extremely configurable.Comment: Presented at the 17th International Conference on Computing in High Energy and Nuclear Physic