The N∗ (1520) → Δπ amplitudes extracted from the γp → π+π−p reaction and comparison to quark models

The γp → π+π−p reaction, in combination with data from the πN → ππN reaction has been recently analyzed and allows one to obtain the s- and d-wave amplitudes for the N∗ (1520) decay into Δπ with absolute sign with respect to the N∗ (1520) → Nγ helicity amplitudes. In addition one obtains the novel information on the momentum dependence of the amplitudes. In the present paper we show how this new information poses new constraints to quark models of hadron structure. In particular we show that the signs and the momentum dependence of these amplitudes coincide with those given by non relativistic constituent quark models. The absolute values provided by these models agree only qualitatively, and a discussion is done on the reasons for it and possible ways to improve.