Omega meson cloud and the proton's light anti-quark distributions

Abstract

We use the meson cloud model of the nucleon to calculate distribution functions for (d −ū) andd/ū in the proton. Including the effect of the omega meson cloud, with a coupling constant g 2 ω /4π ≈ 8, allows a reasonably good description of the data.

Sigma meson cloud and proton's light flavor sea quarks

“…As calculated in [14], we set g 2 ω /4π as 8.1, which is from fitting to dispersion relation descriptions of forward nucleon-nucleon scattering [15,19,25]. The shadowed area shows the results of varying Λ ω value in the hardly changes with adding σ meson cloud, which is consistent with [14], in which Λ ω is set as 1.5 GeV to obtain a good description of data by considering only π and ω effects. In order to have a deep understanding of this, we present the numbers of the related mesons n M in the proton with the different cutoff values in the two works, which are shown in Table 1.…”

“…Also we can see that the change is not enough to explain the data, which guarantees the necessary to consider other flavor symmetric contribution. The inclusion of isoscalar meson ω with a reasonable coupling constant produces a similar improvement in agreement between theory and experiment [14], so does the inclusion of isoscalar meson σ.…”

“…Many explanations have been applied to attack this problem [10,11,12,13], such as effects of ∆ [10,11,12], the influence of the Pauli exclusion principle [12], adjustment of parameters [13], but none of these explanations provides a satisfactory description of the ratio d(x)/u(x). However, Alberg, Henley and Miller [14] found that the inclusion of the effect of the isoscalar vector meson ω, with a coupling constant g 2 ω /4π ≈ 8.1, allows a good description of the data. As mentioned in that article, adding the σ effect will likely improve the description of the data.…”

Electroweak structure of the nucleon, meson cloud, and light-cone wave functions

“…Instead, for the NNω coupling, g N N ω , we used the result from the analysis of Ref. [57] about the ω contribution to the unpolarized anti-quark distributions, which favors a much smaller value for g N N ω than the one used to describe the nucleon scattering data. The numerical values for each of the BM states are summarized in Table I.…”

Improved measurement of thed¯/ūasymmetry in the nucleon sea

“…These models do however indicate that pions make up a large part of the sea where the asymmetry is greatest. In contrast, Alberg et al [56] have investigated whether or not the entire light antiquark sea might be understood in a meson-cloud picture. They find that, by considering πN and ωN contributions, they can fitd(x) −ū(x) and simultaneously obtain a reasonable description ofd/ū at x < 0.25.…”