Strangeness magnetic form factor of the proton in the extended chiral quark model

Abstract

Background: Unravelling the role played by nonvalence flavors in baryons is crucial in deepening our comprehension of QCD. Strange quark, a component of the higher Fock states in baryons, is an appropriate tool to investigate nonperturbative mechanisms generated by the pure sea quark. Purpose: Study the magnitude and the sign of the strangeness magnetic moment ${\mu }_s$ and the magnetic form factor ($G_M^s$) of the proton. Methods: Within an extended chiral constituent quark model, we investigate contributions from all possible five-quark components to ${\mu }_s$ and $G_M^s(Q^2)$ in the four-vector momentum range $Q^2\le 1$ (GeV/c)${}^2$. Probability of the strangeness component in the proton wave function is calculated employing the ${}^3{P}_0$ model. Results: Predictions are obtained without any adjustable parameters. Observables ${\mu }_s$ and $G_M^s(Q^2)$ are found to be small and negative, consistent with the lattice-QCD findings as well as with the latest data released by the PVA4 and HAPPEX Collaborations. Conclusions: Due to sizeable cancelations among different configurations contributing to the strangeness magnetic moment of the proton, it is indispensable to (i) take into account all relevant five-quark components and include both diagonal and non-diagonal terms, (ii) handle with care the oscillator harmonic parameter ${\omega }_5$ and the $s\bar{s}$ component probability.

Comments: References added, typos corrected, accepted for publication by Phys. Rev. C