The spin-dependent structure function g1(x) of the deuteron from polarized deep-inelastic muon scattering

Abstract We present a new measurement of the virtual photon proton asymmetry A1p from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0.0008 1 GeV2. A perturbative QCD evolution in next-to-leading order is used to determine g1p(x) at a constant Q2. At Q2 = 10 GeV2 we find, in the measured range, ∫ 0.003 0.7 g 1 P (x) d x=0.139±0.006 ( stat ) ±0.008 ( syst ) ±0.006( evol ) . The value of the first moment Г 1 P = ∫ 0 1 g 1 p (x) d x of g1p depends on the approach used to describe the behaviour of g1p at low x. We find that the Ellis-Jaffe sum rule is violated. With our published result for Γ1d we confirm the Bjorken sum rule with an accuracy of ≈ 15% at the one standard deviation level.