Nucleon spin structure and quark helicity decomposition.

Abstract

Using the results for the first moments of the proton and deuteron spin structure functions {ital g}{sub 1}{sup {ital p},{ital d}} measured at the SLAC experiment E143, we compare the conventional method of obtaining from those moments the quark helicity contributions to the proton spin assuming SU(3){sub flavor} symmetry (which implies a strange quark sea helicity {Delta}{ital s}{ne}0) to the results obtained assuming {Delta}{ital s}=0. We conclude that current experimental uncertainties cannot rule out the latter. Using {Delta}{ital s}=0 we extract the SU(3){sub flavor} {ital F} and {ital D} terms directly from the first moments, which give an estimate of possible symmetry breaking. {copyright} {ital 1996 The American Physical Society.}