## Abstract

Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a^{6}LiD target. The data were taken at 160 GeV beam energy and the results are shown for the kinematic range 1(GeV/c)^{2}<;Q^{2}<100(GeV/c)^{2}in photon virtuality, 0.004<;x<;0.7 in the Bjorken scaling variable and W>4GeV/c^{2}in the mass of the hadronic final state. The deuteron double-spin asymmetry A_{1}^{d}and the deuteron longitudinal-spin structure function g_{1}^{d}are presented in bins of x and Q^{2}. Towards lowest accessible values of x, g_{1}^{d}decreases and becomes consistent with zero within uncertainties. The presented finalg_{1}^{d}values together with the recently published final g_{1}^{p}values of COMPASS are used to again evaluate the Bjorken sum rule and perform the QCD fit to the g_{1}world data at next-to-leading order of the strong coupling constant. In both cases, changes in central values of the resulting numbers are well within statistical uncertainties. The flavour-singlet axial charge a_{0}, which is identified in the MS‾renormalisation scheme with the total contribution of quark helicities to the nucleon spin, is extracted at next-to-leading order accuracy from only the COMPASS deuteron data: a_{0}(Q^{2}=3(GeV/c)^{2})=0.32±0.02_{stat}±0.04_{syst}±0.05_{evol}. Together with the recent results on the proton spin structure function g_{1}^{p}, the results on g_{1}^{d}constitute the COMPASS legacy on the measurements of g_{1}through inclusive spin-dependent deep inelastic scattering.

Original language | English |
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Pages (from-to) | 34-41 |

Number of pages | 8 |

Journal | Physics Letters B |

Volume | 769 |

DOIs | |

State | Published - 10 Jun 2017 |

## Keywords

- COMPASS
- Deep inelastic scattering
- Parton helicity distributions
- Spin
- Structure function

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