Contributions of qqqq\bar{q} Components to Axial Charges of Proton and N(1440)

The axial charges of the proton and N(1440) are studied in the framework of an extended constituent quark model (CQM) includingqqqq\bar{q} components. The cancellation between the contributions of qqq components and qqqq\bar{q} components gives a natural explanation to the experimental value of the proton axial charge, which can not be well reproduced in the traditional CQM even after the SU(6) \otimes O(3) symmetry breaking is taken into account. The experimental value of axial charge pins down the proportion of the qqqq\bar{q} component in the proton to about 20%, which is consistent with the ones given by the strong decay widths and helicity amplitudes. Besides, an axial charge for N(1440) about 1 is predicted with 30\% qqqq\bar{q} component, which is obtained by the strong and electromagnetic decays.