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. The strange quark, a component of the higher Fock states in baryons, is an appropriate tool to study nonperturbative mechanisms due to the pure sea quark.Purpose: Study the magnitude and the sign of the strangeness magnetic moment ${\ensuremath{\mu}}_{s}$ 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 ${\ensuremath{\mu}}_{s}$ and ${G}_{M}^{s}({Q}^{2})$ in the four-vector momentum range ${Q}^{2}\ensuremath{\le}1$ (GeV/$c$)${}^{2}$. The probability of the strangeness component in the proton wave function is calculated employing the ${}^{3}{P}_{0}$ model.Results: Predictions are obtained by using input parameters taken from the literature. The observables ${\ensuremath{\mu}}_{s}$ 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 sizable cancellations 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 nondiagonal terms, (ii) handle with care the oscillator harmonic parameter ${\ensuremath{\omega}}_{5}$ and the $s\overline{s}$ component probability.