Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 20: Focus Session: QCD@FAIR

HK 20.3: Group Report

Wednesday, March 18, 2026, 14:25–14:45, AM 00.014

Hadron physics studies at the pion beams facility with HADES — •Manuel Lorenz for the HADES collaboration — GSI Helmholtzzentrum für Schwerionenforschung GmbH(GSI) — Goethe University Frankfurt

We present the physics program of π–N and π–A reactions up to √s ≈ 2.35 GeV at the GSI pion-beam facility in combination with the HADES spectrometer. On proton targets, the program enables systematic studies of baryon resonances and their electromagnetic structure up to the third resonance region. Differential cross sections and polarization observables are used in Partial-Wave Analyses to tightly constrain baryon–meson and baryon–virtual-photon couplings, in particular ρ N and ω N. Moreover, e⁺e⁻ measurements probe the electromagnetic transition form factors in the time-like region and clarify the role of vector mesons. On nuclear targets, pion beams provide excellent kinematic conditions, with small relative momenta in the final state, enhancing sensitivity to medium effects. This allows us to explore vector-meson propagation in cold nuclear matter and to study the production of hidden- and open-strangeness particles. The same kinematics are ideally suited to investigate hypernuclei formation from low–relative-momentum strange baryons. In addition, these measurements provide a crucial connection to neutrino-nucleus interaction modeling by delivering high-precision hadronic baselines that constrain the reaction dynamics underlying long-baseline neutrino-oscillation experiments.

Keywords: pion-beam; baryon resonances; electromagnetic structure; in-medium hadron properties; baselines for long-baseline neutrino experiments