The Spin-Dependent Structure Function of the Deuteron

Abstract

The SMC collaboration at CERN has recently measured the spin-dependent structure function g ¹ _d (x) of the deuteron.The data taken cover the kinematical region 1 GeV² < Q ² < 30 GeV² and 0.006 < x < 0.6. The first moment Γ ¹ _d of g ¹ _d is found to be two standard deviations below the prediction of the Ellis-Jaffe sum-rule. The inferred quark contribution to the proton spin is ΔΣ = 0.06 ± 0.20 ± 0.15. When combined with the result of EMC for the proton Γ ¹ _p , the difference Γ ¹ _p − Γ ¹ _n = 0.20 ± 0.05 ± 0.04 is deduced, in good agreement with the fundamental Bjorken sum rule. Comparison with other experiments shows that in the region of x where the measurements overlap, the SMC deuteron data agree with the combination of EMC data for the proton and the recent E142 data for the neutron.

On behalf of the Spin Muon Collaboration