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HK: Fachverband Physik der Hadronen und Kerne

HK 2: Heavy Ion Collision and QCD Phases I

HK 2.2: Talk

Monday, March 14, 2016, 14:30–14:45, S1/01 A01

Studying ρ-N couplings with HADES in pion-induced reactions — •Federico Scozzi for the HADES collaboration — TU Darmstadt — IPN Orsay, France

It has been established that baryon-driven medium effects are the key in describing the low mass excess measured in heavy-ion collisions. Yet to understand better medium effects one needs measurement of electromagnetic transition form factors in the time-like region. The coupling of virtual photons to baryonic resonances can be experimentally probed by means of π⁻ N → R → e⁺e⁻N processes for which no experimental data exist.

In summer 2014 data were taken with the High Acceptance Di-Electron Spectrometer (HADES) at GSI in pion-induced reactions using carbon and polyethylene targets. A large part of the data was taken at a pion beam momentum of 0.69 GeV/c in order to explore the sub-threshold coupling of the ρ to baryonic resonances. Combining polyethylene data with carbon data it is possible to extract pion-proton interactions. In this contribution the preliminary results of inclusive dilepton invariant mass will be presented and compared with model calculations. Finally the exclusive channel π⁻ p → e⁺e⁻n will be discussed in detail.

This work has been supported by VH-NG-823, Helmholtz Alliance HA216/EMMI and GSI.