The role of components in the nucleon and the N(1440) resonance

The role of components in the nucleon and the N(1440) resonance is studied by explicit coupling of the lowest positive parity state to the qqq components in the harmonic oscillator quark model. The lowest energy component, where the 4-quark subsystem has the flavor–spin symmetry [4]FS[22]F[22]S, is close in energy to the lowest positive parity excitation of the nucleon in the qqq quark model. The confining interaction leads to a strong mixing of the system and the positive parity excited state of the qqq system. This result is in line with the phenomenological indications for a two-component structure of the N(1440) resonance. The presence of substantial components in the N(1440) can bring about a reconciliation of the constituent quark model with the large empirical decay width of the N(1440).