Is the Polarized Antiquark Sea in the Nucleon Flavor Symmetric?

Abstract

We show that the model which naturally explains the $\bar{u}\ne \bar{d}$ asymmetry in the nucleon and is in quantitative agreement with the Gottfried sum rule data, also predicts that in the proton $\Delta \bar{u}>0>\Delta \bar{s}>\Delta \bar{d}$ and $\Delta \bar{u}-\Delta \bar{d}>\bar{d}-\bar{u}>0$. At the input scale, these results can be derived even analytically. Thus the violation of the flavor symmetry is more serious in the polarized case than in the unpolarized case. In contrast, many recent analyses of the polarized data have made a simplifying assumption that all the three $\Delta \bar{q}$'s have the same sign and magnitude. We point out the need to redo these analyses, allowing for the alternate scenario as described above. We present predictions of the model for the $W^{-}$ asymmetry in polarized $pp$ scattering, which can be tested at RHIC; these are quite different from those available in the literature.

Comments: Talk given at the International Conference on Quark-Nuclear Physics (QNP2000), 21-25 Feb. 2000, CSSM, University of Adelaide, Australia. v2: refs added, discussion enlarged, conclusions unchanged. A short version has appeared in NP(A) proceedings. This (long) version is to appear in PR(C). Tables of polarized and unpolarized PDFs can be obtained by writing to the Author