Measurement of the Proton Spin Structure Function g₁(x,Q²) for Q² from 0.15 to 1.6 GeV² with CLAS

الأصل · EN

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH₃ target in the CLAS detector. The polarized structure function g₁(x,Q²) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q² = 0.15 -1.64 GeV². The contributions to the first moment Γ₁(Q²) = ∫ g₁(x,Q²)dx were determined up to Q²=1.2 GeV². Using a parametrization for g₁ in the unmeasured low x regions, the complete first moment was estimated over this Q² region. A rapid change in Γ₁ is observed for Q² < 1 GeV², with a sign change near Q² = 0.3 GeV², indicating dominant contributions from the resonance region. At Q²=1.2 GeV² our data are below the pQCD evolved scaling value.