scholarly journals Time-Like Baryon Transitions studies with HADES

2019 ◽  
Vol 199 ◽  
pp. 01008 ◽  
Author(s):  
B. Ramstein ◽  
J. Adamczewski-Musch ◽  
O. Arnold ◽  
B. Arnoldi-Meadows ◽  
A. Belounnas ◽  
...  
Keyword(s):  
Crucial Role ◽  
Vector Mesons ◽  
Pion Beam ◽  
Medium Effects ◽  
Kinematic Range ◽  
Proton Proton ◽  
Dalitz Decay ◽  
Elementary Reactions ◽  
Hades Collaboration ◽  
Beam Experiment

The HADES collaboration uses the e+e− production as a probe of the resonance matter produced in collisions at incident energies of 1-3.5 GeV/nucleon at GSI. Elementary reactions provide useful references for these studies and give information on resonance Dalitz decays (R→Ne+e−). Such processes are sensitive to the structure of time-like electromagnetic baryon transitions in a kinematic range where (off-shell) vector mesons play a crucial role. Results obtained in proton-proton reactions and in a commissioning pion-beam experiment are reported and prospects for future pion beam experiments and for first hyperon Dalitz decay measurements are described. The connection with the investigations of medium effects to be continued with HADES in the next years at SIS18 and SIS100 is also discussed.

scholarly journals Studying time-like electromagnetic baryonic transitions with HADES in pion induced reactions

2020 ◽  
Vol 241 ◽  
pp. 01012
Author(s):  
Béatrice Ramstein
Keyword(s):  
Center Of Mass ◽  
Quantitative Description ◽  
Form Factors ◽  
Resonance Region ◽  
Partial Wave Analysis ◽  
Real Photon ◽  
Pion Beam ◽  
Dalitz Decay ◽  
Covariant Model ◽  
Proton Induced Reactions

A dedicated programme aiming at studying electromagnetic baryonic transitions in the time-like region has started at GSI using the pion beam and the High Acceptance Di-Electron Spectrometer (HADES) set-up. A pioneering experiment has been carried out in the second resonance region, at a center-of-mass energy of 1.49 GeV, using carbon and polyethylene targets, allowing for an analysis of the inclusive e+e- production and of the exclusive quasi-free π-p → ne+e- reaction, in complement to hadronic channels. Predictions for the Dalitz decay of N(1520) and N(1535) based on real photon couplings strongly underestimate the e+e- yield at invariant masses larger than 300 MeV/c2, which signals effects of time-like baryon transition form factors, in qualitative agreement with the Vector Dominance Models (VDM). A quantitative description of the observed e+e- yield is achieved by taking into account the contribution from off-shell ρs. The latter was provided by the preliminary results of a Bonn-Gatchina Partial Wave Analysis of the two-pion production channels, which were measured simultaneously in our experiment. A good agreement is also obtained using a covariant model for the time-like electromagnetic form factors for the N-N(1520) transition. The angular distributions for the e+e- production contain additional selective information on the spin structure of the different transitions. The measurements with the pion beam will be extended in future in the third resonance region. Hyperon Dalitz decay studies in proton induced reactions are also foreseen.

scholarly journals Search for medium effects on light vector mesons

2007 ◽  
Author(s):  
C. Djalali ◽  
R. Nasseripour ◽  
D. P. Weygand ◽  
M. H. Wood ◽  
Keyword(s):  
Vector Mesons ◽  
Medium Effects ◽  
Light Vector

scholarly journals Δ(1232) Dalitz decay in proton-proton collisions at T=1.25 GeV measured with HADES at GSI

2017 ◽  
Vol 95 (6) ◽  
Author(s):  
J. Adamczewski-Musch ◽  
O. Arnold ◽  
E. T. Atomssa ◽  
C. Behnke ◽  
A. Belounnas ◽  
...  
Keyword(s):  
Proton Proton ◽  
Dalitz Decay ◽  
Proton Collisions ◽  
Proton Proton Collisions

scholarly journals Medium effects in the production and decay of vector mesons in pion-nucleus reactions

1997 ◽  
Vol 625 (4) ◽  
pp. 832-854 ◽  
Author(s):  
Ye.S. Golubeva ◽  
L.A. Kondratyuk ◽  
W. Cassing
Keyword(s):  
Vector Mesons ◽  
Medium Effects

DILEPTON PRODUCTION IN HEAVY ION REACTIONS

2007 ◽  
Vol 16 (03) ◽  
pp. 879-890 ◽  
Author(s):  
AMAND FAESSLER ◽  
CHRISTIAN FUCHS
Keyword(s):  
Vector Meson ◽  
Heavy Ion ◽  
Vector Mesons ◽  
Dilepton Production ◽  
Medium Effects ◽  
Heavy Ion Reactions ◽  
Nucleon Resonances ◽  
Unified Description

We present a unified description of the vector meson and dilepton production in elementary and in heavy ion reactions. The production of vector mesons is described via the excitation of nucleon resonances. Medium effects in heavy ion reactions are discussed.

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