Electromagnetic Properties of S ₁₁ States in a Light Cone Quark Model

Abstract

Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S11 resonances, N(1535) and N(1650), and the helicity amplitudes A1/2 and S1/2 for electroexcitation of the S11 resonances from the nucleon. The electromagnetic form factors of these S11 resonances are found to be similar to those of the nucleon in shape, while the charge form factor of neutral N(1650) is nearly zero. The relative peak height of the S11 charge form factors is controlled by the mixing angle common to both resonance wave functions. As in most quark models, there is a systematic overestimate of A1/2p in both N(1535) and N(1650) cases at the photon point. A sizeable S1/2 for all cases is produced as suggested by experiments.

Covariant model for theγN→N(1535)transition at high momentum transfer

“…We will start by discussing the constituent quark models. Different quark model predictions, including nonrelativistic [15,16,[19][20][21] and relativistic [18,[23][24][25] formulations, agree qualitatively with the data for A 1=2 . In particular, in Ref.…”

“…They are based either on quark models or on effective meson-baryon interaction models. In the first case, there are nonrelativistic constituent quark models [4,5,[15][16][17][18][19][20][21][22], relativistic quark models [18,[23][24][25], quark models with explicit quark-antiquark contributions [26], and QCD sum rules [27]. Alternatively, in the second case, the Nð1535Þ is interpreted as a molecular-type state dynamically generated by the meson-nucleon interaction [28][29][30][31][32][33][34][35][36][37] with a particular dominance of the KAE quasibound state [28,29,32].…”