Abstract
The unambiguous identification of hadron modifications in hot and dense QCD matter is one of the important goals in nuclear physics. In the regime of 1 - 2 GeV kinetic energy per nucleon, HADES has measured rare and penetrating probes in elementary and heavy-ion collisions. The main creation mechanism of mesons is the excitation and decay of baryonic resonances throughout the fireball evolution. The reconstruction of shortlived (≈ 1 fm/c) resonance states through their decay products is notoriously difficult. We have developed a new iterative algorithm, which builds the best hypothesis of signal and background by distortion of individual particle properties. This allows to extract signals with signal-to-background ratios of <1%.
Highlights
The mechanism of mass generation of hadrons stays an open question
In AA collisions, depending on the energy and system size, chiral symmetry can be partially restored. These changes are reflected in the modification of the spectral functions of hadrons
It was shown that from relativistic (SIS18, SPS, AGS) to ultra-relativistic collisions (RHIC, LHC) baryons and anti-baryons play an important role in the modification of the spectral functions of the ρ, ω and φ mesons [2]
Summary
The mechanism of mass generation of hadrons stays an open question. the Higgs mechanism successfully explains mass generation of the three families of fermions, leptons and quarks, and the electroweak gauge bosons W± and Z, the way how matter, i.e. neutrons and protons, obtains its mass remains unclear. In AA collisions, depending on the energy and system size, chiral symmetry can be partially restored These changes are reflected in the modification of the spectral functions of hadrons. It was shown that from relativistic (SIS18, SPS, AGS) to ultra-relativistic collisions (RHIC, LHC) baryons and anti-baryons play an important role in the modification of the spectral functions of the ρ, ω and φ mesons [2]. One can observe these modifications best in the di-lepton decay channel, it might be that reconstruction of π+π− decays could provide valuable information as well [3].
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