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

The role of qq¯ components in the nucleon and the N(1440) resonance is studied by explicit coupling of the lowest positive parity qqqqq¯ state to the qqq components in the harmonic oscillator quark model. The lowest energy qqqqq¯ component, where the 4-quark subsystem has the flavor-spin symmetry [4[22[22, 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 qqqqq¯ 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 qq¯ 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).