Role of the qqqqq̄ components in the electromagnetic transition

The helicity amplitudes A 1/2 and S 1/2 for the electromagnetic transition γ∗N → N∗(1535) are calculated in the quark model that is extended to include the lowest lying qqqqq̄ components in addition to the qqq component. It is found that with admixture of 5-quark components with a proportion of 20% in the nucleon and 25-65% in the N∗(1535) resonance the calculated helicity amplitude A 1/2 decreases at the photon point, Q = 0 to the empirical range. The qqqqq̄ components contain ss̄ pairs, which is consistent with the substantial width for Nη decay of the N∗(1535). The best description of the momentum dependence of the empirical helicity amplitudes is obtained by assuming that the qqqqq̄ components are more compact than the qqq component. However, this version of extended quark model still does not lead to a satisfactory simultaneous description of both A 1/2 and S 1/2 although with significant improvement. PACS. 12.39.Jh Nonrelativistic quark model – 14.20.Gk Baryon resonances with S=0