Abstract

The High Acceptance Di-Electron Spectrometer (HADES) installed at GSI in Darmstadt and de signed to investigate dielectron production in heavy-ion collisions in the range of kinetic beam energies 1-3 A GeV is also an excellent detector for charged hadron detection. We discuss the analysis of thepp → ppπ+π-channel at an incident energy of 3.5 GeV, using results from pp→ppπ0, pp→pnπ+andpp → pKΛ measured at the same energy by HADES. A consistent description of the differential cross sections as a function of the invariant mass and the production angles is achieved by a simple resonance model taking into account the single and the double excitation of baryonic resonances with masses up to 1.9 GeV. The contributions can be quantified and confronted to the inputs of transport models or to the predictions of dedicated models for nucleon-nucleon reactions. In addition, using specific kinematical cuts, the total production cross section and the angular dis tribution of the ρ meson have been also extracted. As both baryon resonances and the ρ meson are important sources of di-electrons, these results will provide valuable constraints for the interpretation of the dielectron spectra measured by the HADES collaboration.

Highlights

  • The High Acceptance DiEelectron Spectrometer (HADES) [1] installed at GSI in Darmstadt was built to investigate dielectron production in order to study the hot and dense hadronic medium produced in heavy-ion collisions in the 1-2 AGeV energy range

  • According to Vector Meson Dominance [3], electromagnetic transitions between hadrons are mediated by vector mesons, which strongly connects the Dalitz decay of baryons to their coupling to vector mesons

  • These preliminary results show the interest of the pp → ppπ+π− reaction to constrain in a quantitative way the baryon resonance contribution and the ρ meson production, which are important sources of e+e− pairs

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Summary

Introduction

The High Acceptance DiEelectron Spectrometer (HADES) [1] installed at GSI in Darmstadt was built to investigate dielectron production in order to study the hot and dense hadronic medium produced in heavy-ion collisions in the 1-2 AGeV energy range. The possibility to measure simultaneously with the HADES detector meson and di-electron production is a great advantage In this way, constraints on reaction mechanisms, and in particular on the role of intermediary baryon resonances, obtained by the study of the meson production channels can be used for the interpretation of the dielectron production. Constraints on reaction mechanisms, and in particular on the role of intermediary baryon resonances, obtained by the study of the meson production channels can be used for the interpretation of the dielectron production This motivated previous studies of the HADES collaboration in the 1π, η, KΛ and KΣ production channels in pp reactions from 1.25 to 3.5 GeV [4,5,6,7]. The reaction is well suited to study the single and double excitation of many baryon resonances the production of the ρ meson, either directly or via the decay of baryon resonances

Previous HADES studies
HADES resonance model
Findings
Conclusion
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