Mesonic corrections to the shape of quark distributions

Abstract

We compute the full x -dependence of the proton and neutron spin structure functions in the MIT bag model, including the effect of gluon exchange and the meson cloud. Impressive agreement is found for x larger than 0.1, where polarised gluons are not expected to play a significant role.

Strangeness in the nucleon on the light cone

“…By carrying away some orbital angular momentum of the nucleon, a kaon cloud could naively be expected to reduce the intrinsic spin carried by quarks, and give rise to a negatively polarized strange quark distribution, ∆s(x, µ 2 ). The effect of the meson cloud on the polarized nucleon quark distributions has been addressed by several authors [15,22,46]. Although the kaon cloud picture can provide a simple framework within which the non-perturbative sea could be understood qualitatively, it is clearly important to determined whether such a picture can provide, or even be consistent with, a more quantitative description.…”

Baryonic masses based on the NJL model

“…(very close to our net pressure with parameter set 2) was more appropriate for the hadronic structure functions [25]. In order to have equilibrium, the effective vacuum pressure and the three quark pressure (20) must be equal; by imposing this condition we can then fix the parameter b in terms of the NJL model parameters.…”

The Spin Dependent Structure Functions of the Nucleon

“…As can be seen in figure 11, the fit to the experimental data is considerably improved by including both the polarized gluon distribution and meson cloud effects. It is known [30,63] that the meson cloud lowers the bag model calculation for g p 1 over the entire range of x since the angular momentum of the meson cloud carries some of the spin of the nucleon. However these calculations overestimate g p 1 (x) in the region x < 0.1 and give results with much smaller magnitude than the experimental data for g n 1 (x) in the region x < 0.2.…”