The strangeness form factors of the proton within nonrelativistic constituent quark model revisited

摘要

We reexamine, within the nonrelativistic constituent quark model (NRCQM), a recent claim that the current data on the strangeness form factors indicates that the uudss? component in the proton is such that the uuds subsystem has the mixed spatial symmetry [31]X and flavor spin symmetry [4]FS[22]F[22]S, with s? in S state (configuration I). We find this claim to be invalid if corrected expressions for the contributions of the transition current to G_A~s and G_E~s are used. We show that, instead, it is the lowest-lying uudss? configuration with uuds subsystem of completely symmetric spatial symmetry [4]_X and flavor spin symmetry [4]FS[22]F[22]S, with s? in P state (configuration II), which could account for the empirical signs of all form factors G_E~s, G_M~s, and G_A~s. Further, we find that removing the center-of-mass motion of the clusters will considerably enhance the contributions of the transition current. We also demonstrate that it is possible to give a reasonable description of the existing form factors data with a tiny probability PP_(ss?)=0.025% for the uudss? component. We further see that with a small admixture of configuration I, the agreement of our prediction with the data for G_A~s at low- q~2 region can be markedly improved. We find that without removing CM motion, P_(ss?) would be overestimated by about a factor of four in the case when transition current dominates. We also explore the consequence of a recent estimate reached from analyzing the existing data on d?-ū, s+s?, and ū+d?-s-s?, that Pss? lies between 2.4-2.9%. It would lead to a large size for the five-quark system and a small bump in both G_E~s+ηG_M~s and G_E~s in the region of q~2>0.1 GeV~2 within the considered model.