We present the final results of the spin asymmetries A1 and the spin structure functions g1 of the proton and the deuteron in the kinematic range 0.0008<x<0.7 and 0.2<Q2<100GeV2. For the determination of A1, in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new method which minimizes the radiative background by selecting events with at least one hadron as well as a muon in the final state. We find that this hadron method gives smaller errors for x<0.02, so it is combined with the usual method to provide the optimal set of results.
The virtual photon proton asymmetries.
The virtual photon deuteron asymmetries.
The virtual photon proton asymmetries in smaller X and Q**2 bins. bins. Errors are statistical only.
We present a new measurement of the spin-dependent structure function g 1 d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 < x < 0.7 and 1 GeV 2 < Q 2 < 60 GeV 2 . This structure function is found to be negative at small x . The first moment Γ 1 d =∫ 0 1 g 1 d d x evaluated at Q 0 2 = 10 GeV 2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Γ 1 p , we obtain Γ 1 p − Γ 1 n = 0.199 ± 0.038 which agrees with the Bjorken sum rule.
Results on the virtual photon deuteron asymmetry.
Results on the spin structure function of the deuteron.
Results on the spin structure function of the neutron.
The spin-dependent structure function g 1 p has been measured by deep inelastic scattering of polarized muons off polarized protons at 190 GeV incident muon energy. The data cover a kinematic range of 1 < Q 2 < 80 GeV 2 and 0.003 < x < 0.6, where −Q 2 is the squared 4-momentum transfer and x is the Biorken scaling variable. The first moment Γ 1 p = ∫ 0 1 g 1 p d x = 0.152 ± 0.015( stat. ) ± 0.018( syst. ) is smaller than the prediction of the Ellis-Jaffe sum rule by one standard deviation. This result leads to a contribution of the quark spins to the proton spin of δΣ = 0.36 ± 0.21. All results presented here are preliminary.
First moment of the spin-dependent structure function G1.
SMC is progressing a series of experiments to reveal the spin structure of nucleon at CERN. The first experiment on deuteron has been performed in 1992. We will report here the data on deuteron and discuss the present status of nucleon spin structure using all data including SMC and also E142(SLAC) data recently reported.
First moment of the spin-dependent structure function G1.
We report on the first measurement of the spin-dependent structure function g 1 d of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006< x <0.6, 1 GeV 2 < Q 2 <30 GeV 2 . The first moment, Γ 1 d =ʃ 0 1 g 1 d d x=0.023±0.020 ( stat. ) ± 0.015 ( syst. ) , is smaller than the prediction of the Ellis-Jaffe sum rules. Using earlier measurements of g 1 p , we infer the first moment of the spin-dependent neutron structure function g 1 n . The difference Γ 1 p − Γ 1 n =0.20±0.05 (stat.) ± 0.04 (syst.) agrees with the prediction of the Bjorken sum rule, Γ 1 p − Γ 1 n =0.191±0.002.
Virtual photon asymmetry A1.
Spin-dependent structure function G1.
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