Photo- and electro-production of mesons on nucleons and nuclei

In these lectures I will show some results obtained with the chiral unitary approach applied to the photo- and electro-production of mesons. The results for the photo-production of ηπ0pηπ0p and K0π0Σ+K0π0Σ+, together with related reactions will be shown, having with common denominator the excitation of the Δ(1700)Δ(1700) resonance which is one of those dynamically generated in the chiral unitary approach. Then I will show the results obtained for the e+e−→ϕf0(980)e+e−→ϕf0(980) reaction which reproduce the bulk of the data except for a pronounced peak, giving support to a new mesonic resonance, X(2175). Results will also be shown for the electromagnetic form factors of the N∗(1535)N∗(1535) resonance, also dynamically generated in this approach. Finally, I will show some results on the photo-production of the ωω in the nuclei, showing that present experimental results claiming a shift of the ωω mass in the medium are tied to a particular choice of background and are not conclusive. On the other hand, the same experimental results show unambiguously a huge increase of the ωω width in the nuclear medium.