NEUTRON SPIN-DEPENDENT STRUCTURE-FUNCTION, BJORKEN SUM-RULE, AND FIRST EVIDENCE FOR SINGLET CONTRIBUTION AT LOW X

We perform the isospin decomposition of proton and neutron SLAG data f or moderately low x in the region 0.01 less than or equal to x less th an or equal to 0.1. The isovector part is well described by a power be havior x(alpha), where alpha does not correspond to the intercept of a single a(1) Regge trajectory, as expected. However, the observed powe r leads to the validity of the Bjorken sum rule and it is consistent w ith the power extracted from al previous data using next-to-leading or der evolution. At the same time, the isoscalar behavior may be interpr eted as a partial cancellation between a positive nonsinglet contribut ion and a strongly negative singlet one. Further experimental conseque nces are mentioned.