https://doi.org/10.1140/epja/i2002-10161-2
Short Note
Polarized antiquark flavor asymmetry $\mathrm{\Delta \bar u (x) - \Delta \bar d(x)}$ and the pion cloud
1
Institut für Theoretische Physik, Universität Regensburg, D-93053, Regensburg, Germany
2
Physics Department, Duke University, P.O. Box 90305, NC 27708, Durham, USA
* e-mail: christian.weiss@physik.uni-regensburg.de
The flavor asymmetry of the unpolarized antiquark distributions in the proton, $\bar u(x) - \bar d(x) < 0$, can qualitatively be explained as an effect of the pion cloud. Corresponding predictions have been made for the polarized asymmetry, $\Delta \bar u(x) - \Delta \bar d(x)$, based on rho-meson contributions. These estimates differ in sign and magnitude from those obtained in quark-based models, which give $\Delta \bar u(x) - \Delta \bar d(x) > 0$. Using a simple chiral linear sigma model as an example, we demonstrate that in the meson cloud picture a large positive $\Delta \bar u(x) - \Delta \bar d(x)$ can be obtained from $\pi$-$\sigma$ interference contributions. This calls into question previous estimates based on rho-meson contributions alone, and indicates how the results of the meson cloud picture may be reconciled with those of quark-based models.
© Società Italiana di Fisica and Springer-Verlag, 2003
