Abstract
We have performed a study of the isovector, octet and singlet axial charges of the proton in an extended chiral constituent quark model, where all the possible $uudq\bar{q}$~($q=u,d,s$) five-quark Fock components in the proton wave function are taken into account. The $^3P_0$ quark-antiquark creation mechanism is assumed to account for the transition coupling between three- and five-quark components in proton, and the corresponding transition coupling strength is fixed by fitting the intrinsic sea flavor asymmetry $\bar{d}-\bar{u}$ data for proton. Accordingly, with all the parameters fixed by empirical values, the probabilities of the intrinsic five-quark Fock components in proton wave function should be $\sim30 - 50\%$, which lead to the numerical results for quark spin $\Delta u$, $\Delta d$ and $\Delta s$, as well the axial charges of proton consistent with the experimental data and predictions by other theoretical approaches.
Highlights
Study of the structure of nucleon and nucleon excitations is one of the most important topic in hadronic physics
We have performed a study of the isovector, octet, and singlet axial charges of the proton in an extended chiral constituent quark model, where all the possible uudqq (q 1⁄4 u, d, s) five-quark Fock components in the proton wave function are taken into account
The 3P0 quark-antiquark creation mechanism is assumed to account for the transition coupling between three- and five-quark components in proton, and the corresponding transition coupling strength is fixed by fitting the intrinsic sea flavor asymmetry d − udata for proton
Summary
Study of the structure of nucleon and nucleon excitations is one of the most important topic in hadronic physics. [2,11], it was shown that the flavor-singlet, isovector, and SU(3) octet axial charges of proton, can be obtained by combining the deep inelastic scattering (DIS) data with the nucleon and hyperon β-decay data, which are: gðA0Þ 1⁄4 0.120 Æ 0.093 Æ 0.138, gðA3Þ 1⁄4 1.254 Æ 0.006, gðA8Þ 1⁄4 0.688 Æ 0.035. These values are obviously different with the constituent quark model predictions which are gðA0Þ 1⁄4 1, gðA3Þ 1⁄4 5=3, and gðA8Þ 1⁄4 1, respectively.
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