Simple relation between the γN→N(1535) helicity amplitudes

It is shown that the helicity amplitudes A1/2 and S1/2 in the γN→N(1535) reaction, can be well related by S1/2=-(√(1+τ)/√(2))(MS2-M2/2MSQ)A1/2 in the region Q2>2 GeV2, where M and MS are the nucleon and N(1535) masses, q2=-Q2 the four-momentum transfer squared, and τ=(Q2/(MS+M)2). This follows from the fact that the Pauli-type transition form factor F2* extracted from the experimental data, turns up to show F2*≅0 for Q2>1.5 GeV2. The observed relation is tested by the experimentally extracted helicity amplitudes and the MAID parametrization (Mainz group). A direct consequence of the relation is that the assumption |A1/2|>>|S1/2| is not valid for high Q2. Instead, both amplitudes A1/2 and S1/2 have the same Q2 dependence in the high Q2 region; aside from that S1/2 has an extra factor, -(1/√(2))(MS-M/2MS). The origin of this relation is interpreted in a perspective of a quark model.