Quark Sea Effect on Static Properties of Hadron.

We study the effect of the quark sea on static properties of hadrons, within the framework of QCD. A QCD Hamiltonian density is used to obtain the quark amplitudes and probability in the lowest-order perturbation theory. The numerical results are obtained by using MIT bag model wavefunctions. A large excitation parameter for sea quark is found. The expectation values for the axial charge g(,A), the proton magnetic moment (mu)(,p), the proton mean-square radius <r(,em)('2)>(,p), and the mean-square radius of the axial charge <r(,ax)('2)> are obtained. Calculations have been done up to the second order of the coupling constant (alpha)(,c) = g('2)/(4(pi)). The results are found to be in rough agreement with experiment for g(,A) and <r(,em)('2)>(,p). The calculated values for (mu)(,p) and <r(,ax)('2)> are found to be smaller than the empirical values by 25%. Employing an approximate Hamiltonian matrix, the wave-functions and operator matrix elements are then calculated exactly. This modifies the excitation parameters for sea quarks. But the renormalized results for four calculated properties remain roughly the same.