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Volume 297 - XXV International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2017) - WG6 Spin and 3D Structure
Final COMPASS results on the spin-dependent structure functions $g_1^p$ and $g_1^d$ in the deep-inelastic and nonperturbative regions
B. Badelek* on behalf of the COMPASS Collaboration
*corresponding author
Full text: pdf
Pre-published on: 2017 September 12
Published on: 2018 January 16
Abstract
This paper summarizes the COMPASS Collaboration legacy on
measurements of the proton and deuteron spin-dependent structure functions, g1p and g1d at Q2<1 GeV2 and Q2>1 GeV2. In both regions and at the lowest measured x, g1d(x) is consistent with zero while g1p(x) is positive. This is the first time that the spin effects are observed at such low values of x. The NLO QCD fit of g1 world data gives well constrained quark helicity distributions; gluons are poorly determined. Quark helicity contribution to nucleon spin is 0.26 < DeltaSigma < 0.36. From the COMPASS data alone the Bjorken sum rule is verified to 9% accuracy and the extracted flavour-singlet axial charge is a_0(Q^2 = 3 GeV2)=0.32 +-0.02 (stat.) +-0.04 (syst) +- 0.05 (evol).
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