Nucleon spin structure and quark helicity decomposition

Abstract

Using the results for the first moments of the proton and deuteron spin structure functions glp,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)flavor symmetry (which implies a strange quark sea helicity Δs≠0) to the results obtained assuming Δs=0. We conclude that current experimental uncertainties cannot rule out the latter. Using Δs=0 we extract the SU(3)flavor F and D terms directly from the first moments, which give an estimate of possible symmetry breaking.