The structure functions F p 2 and F d 2 measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006⩽ x ⩽0.6 and 0.5⩽ Q 2 ⩽55GeV 2 , and include the first precise data at small x , where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results.
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Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004<x<0.8 and 0.4<Q2<190 GeV2, together with the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x)-F2n(x). The value of the Gottfried sum F(F2p-F2n)dx/x=0.240±0.016 is below the quark-parton-model expectation of 1/3.
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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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The Q 2 dependence of the structure function ratio F 2 Sn / F 2 C for 0.01 < x < 0.75 and 1 < Q 2 < 140 GeV 2 is reported. For x < 0.1 the size of shadowing decreases with ln Q 2 and the maximum rate is about 0.04 at x = 0.01. The rate decreases with x and is compatible with zero for x ⩾ 0.1. The difference R Sn − R C , where R is the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, is also given. No dependence on x is seen and the average value is 0.040 ± 0.021 (stat.) ± 0.026 (syst.) at a mean Q 2 of 10 GeV 2 .
Measured values of the difference in the ratios (R) of the longitudinally to transverse polarized virtual photon absorption cross sections R(SN) - R(C).
The proton and deuteron structure functions F2p and F2d were measured in the kinematic range 0.006<x<0.6 and 0.5<Q~2<75 GeV~2, by inclusive deep inelastic muon scattering at 90, 120, 200 and 280 GeV. The measurements are in good agreement with earlier high precision results. The present and earlier results together have been parametrised to give descriptions of the proton and deuteron structure functions F2 and their uncertainties over the range 0.006<x<0.9.
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The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
Results are presented on the difference in R , the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by comparing the ratio of cross sections for the deep inelastic scattering of muons from deuterium and hydrogen targets at 90 and 280 GeV incident energy. The results cover the range x =0.01–0.30, at an average Q 2 of 9 GeV 2 . The measured difference R d - R p shows no significant x dependence and is compatible with zero, as well as with expectations from perturbative QCD. We use the same method to obtain the difference R Ca - R C from cross section ratios measured on carbon and calcium targets at 90 and 200 GeV incident energy.
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Average overall x values.
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 structure function ratiosF2C/F2Li,F2Ca/F2Li andF2Ca/F2C were measured in deep inelastic muonnucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085<x<0.6 and 0.8<Q2<17GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.
Overall normalization error of 0.7%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.8%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.5%, due to uncertainties in target thickness, not included in the table.
Results are presented for six nuclei from Be to Pb on the structure function ratios F 2 A / F 2 C ( x ) and their A dependence in deep inelastic muon scattering at 200 GeV incident muon energy. The data cover the kinematic range 0.01 < x < 0.8 with Q 2 ranging from 2 to 70 GeV 2 . The A dependence of nuclear structure function ratios is parametrised and compared to various models.
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