The energy distribution of inclusive hadrons produced by 280 GeV muons on hydrogen and deuterium targets are compared. The sum of the scaled energy distributions of the positive and negative hadrons is found to be the same for the two targets. The difference of these distributions is observed to factorise inx andz and thez-dependence is found to be independent of the target type and have a form (1−z)2.1±0.2. The net charge of the hadronic jet is positive at highx even in the case when the scattering takes place on the neutron. These results are in good agreement with the expectations of the Quark Parton Model.
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Measurements have been made of the inclusive scattering of 96, 147, and 219 GeV muons from hydrogen, and of 147 GeV muons from deuterium. Results are presented for the nucleon structure function F2(x,Q2) [≡νW2(x,Q2)] for 10<ν<200 GeV and 0.2<Q2<80 GeV2. The value of F2 rises with Q2 at small x, and falls with Q2 at large x, in agreement with the ideas of quantum chromodynamics. An average value of the ratio σLσT≡R=0.52±0.35 has been obtained for the region 0.003<x<0.10 and 0.4<Q2<30 GeV2. The values of F2 from this experiment have been combined with those from other charged-lepton scattering experiments to determine moments of the structure functions. The variation with Q2 of these moments is used to derive values for Λ, taking into account corrections up to second order in αs. The fit to the data is very good.
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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.
The spin asymmetry in deep inelastic scattering of longitudinally polarised muons by longitudinally polarised protons has been measured over a large x range (0.01< x <0.7). The spin-dependent structure function g 1 ( x ) for the proton has been determined and its integral over x found to be 0.114±0.012±0.026, in disagreement with the Ellis-Jaffe sum rule. Assuming the validity of the Bjorken sum rule, this result implies a significant negative value for the integral of g 1 for the neutron. These values for the integrals of g 1 lead to the conclusion that the total quark spin constitutes a rather small fraction of the spin of the nucleon.
THE AVERAGE VALUES OF Q**2 IN EACH X-BIN ARE AS FOLLOWS: X=0.015,Q2=3.5: X=0.025,Q2=4.5: X=0.035,Q2=6.0: X=0.050,Q2=8.0: X=0.078,Q2=10.3: X=0.124,Q2=12.9: X=0.175,Q2=15.2: X=0.248,Q2=18.0: X=0.344,Q2=22.5: X=0.466,Q2=29.5.
The proton structure function F 2 has been measured in the range 2.5 ⪕ Q 2 ⪕ 170 GeV 2 and 0.03 ⪕ x ⪕ 0.65 . Scaling violation is clearly seen in the data. Results of fits to leading-order QCD are presented, together with values of the scale-breaking parameter λ.
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The ratio of the structure function F 2 n / F 2 p ( x ) has been measured in deep inelastic scattering of 274 GeV muons on hydrogen and deuterium targets exposed simultaneously to the beam. The results were obtained from 0.3 (0.6) million events from hydrogen (deuterium) in the range 0.004 < x < 0.8 and 1 < Q 2 < 190 GeV 2 . At x < 0.25 both the statistical and the systematic error is below 2%. Implications for parton distributions and for the σ w / σ z production cross section ratio in p p collisions are discussed. When compared to other results obtained at lower energies, the data indicate a Q 2 dependence of the ratio.
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Results are presented for F2d/F2p and Rd-Rp from simultaneous measurements of deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120, 200 and 280 GeV. The difference Rd-Rp, determined in the range 0.002<x<0.4 at an average Q^2 of 5 GeV^2, is compatible with zero. The x and Q^2 dependence of F2d/F2p was measured in the kinematic range 0.001<x<0.8 and 0.1<Q^2<145 GeV^2 with small statistical and systematic errors. For x>0.1 the ratio decreases with Q^2.
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Results are presented on the ratio of neutron and proton structure functions, F 2 n / F 2 p , deduced from deep inelastic scattering of muon from hydrogen and deuterium. The data, which were obtained at the CERN muon beam at 90 and 280 GeV incident energy, cover the kinematic range x = 0.002−0.80 and Q 2 = 0.1−190 GeV 2 . The measured structure function ratios have small statistical and systematic errors, particularly at small and intermediate x . The observed Q 2 dependence in the range x = 0.1−0.4 is stronger than predicted by perturbative QCD. From the present data together with results from other experiments it is suggested that the twist-four coefficient for the proton is smaller than that for the neutron for x larger than 0.2.
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Merged 90 and 280 GeV data.
The inelastic scattering of muons has been measured using positive muons of momentum 10 GeV/c incident upon a liquid-hydrogen target. We present values of the differential cross section and of the virtual photon-photon absorption cross section for |q| in the range 0.05 to 1.2 (GeV/c)2 and for equivalent photon laboratory energies of 0.6 to 6.5 GeV.
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