Symmetries in hadron physics
Résumé
This contribution, in the field of hadron physics, highlights two aspects of the structure of the nucleon, in its ground and excited states: the sensitivity of the tensor analyzing power for the process d→+p→d+X to the longitudinal form factor of an excited state, the Roper resonance, calculated in the frame of the algebraic collective model for the electroexcitation of nucleon resonances; - the electromagnetic proton form factor, given by a model based on vector meson dominance. This model predicted the decrease of the electric to magnetic proton form factor ratio, well before precise data appeared and it contains the necessary analytical properties to be extended to the annihilation region, where theory and experiment know important developments today.