442 research outputs found
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 and density 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
Thermal dileptons as QCD matter probes at SIS
Electromagnetic radiation is emitted during the whole course of a heavy-ion collision and can escape from the collision zone without further interactions. This makes it an ideal tool to study the properties of hot and dense QCD matter. To model the space-time evolution of the collision at SIS energies a coarse-graining approach is used to convert transport simulations into meaningful temperatures and densities. These parameters serve as input for the determination of the pertinent radiation of thermal dileptons based on an in-medium Ï spectral function that describes available spectra at ultrarelativistic collision energies. The resulting excitation function of the thermal excess radiation provides a baseline for future measurements by the HADES and CBM experiments at GSI/FAIR, and experiments proposed at NICA and J-PARC
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