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.
No description provided.
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No description provided.
A measurement of the nucleon structure function F 2 on iron is presented. The data cover a kinematic range of 3.25 ⪕ Q 2 ⪕ 200 GeV 2 and 0.05 ⪕ x ⪕ 0.65 . The data clearly show scaling violation. Fits in leading-order QCD have been made and values for the scale breaking parameter λ are given.
No description provided.
The x and Q 2 dependence of the single photon exchange cross section d 2 σ /d Q 2 d x and the proton structure functions F 2 ( x , Q 2 ) and R ( x , Q 2 ) have been measured in deep inelastic muon proton scattering in the region 0.02 < x < 0.8 and 3 < Q 2 < 190 GeV 2 . By comparing data at different incident muon energies R was found to have little kinematic dependence and an average value of −0.010 ± 0.037 (stat.) ± 0.102 (stat.). The observed deviations from scaling gave the value of Λ MS , the QCD mass scale parameter, to be 105 −45 +55 (stat.) −45 +85 (syst.) MeV. The fraction of the momentum of the nucleon carried by gluons was found to be ∼56% at Q 2 ∼22.5 GeV 2 . It is shown that to obtain a description of the data for F 2 ( x , Q 2 ) together with that measured in deep inelastic electron-proton scattering at lower Q 2 it is necessary to include additional higher twist contributions. The value of Λ MS remains unchanged with the inclusion of these contributions which were found to have an x -dependence of the form x 3 /(1 − x ).
No description provided.
The reduced cross sections for ep deep inelastic scattering have been measured with the ZEUS detector at HERA at three different centre-of-mass energies, 318, 251 and 225 GeV. From the cross sections, measured double differentially in Bjorken x and the virtuality, Q^2, the proton structure functions FL and F2 have been extracted in the region 5*10^-4 < x <0.007 and 20 < Q^2 < 130 GeV^2.
The reduced cross section at Q**2 = 24 GeV**2 for centre-of-mass energy 318.
The reduced cross section at Q**2 = 32 GeV**2 for centre-of-mass energy 318.
The reduced cross section at Q**2 = 45 GeV**2 for centre-of-mass energy 318.
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.
Additional normalisation error of 0.002 in the ratio.
Additional normalisation error of 0.002 in the ratio.
Additional normalisation error of 0.003 in the ratio.
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.
No description provided.
We present results on a high statistics study of the nucleon structure functions F 2 ( x , Q 2 ) and R = σ L / σ T measured in deep inelastic scattering of muons on a deuterium target. The analysis is based on 8×10 5 events after all cuts, recorded at beam energies of 120, 200 and 280 GeV in the kinematic range 0.06⩽ × ⩽0.80 and 8GeV 2 ⩽ Q 2 ⩽260GeV 2 . Scaling violations observed in the data are in agreement with predictions of perturbative QCD and allow to determine the QCD mass scale parameter Λ.
R=SIG(L)/SIG(T) is taken to be R(QCD).
Small angle scattering of 280 GeV positive muons by deuterium, carbon and calcium has been measured at scattering angles down to 2 mrad. The nucleon structure function F 2 extracted from deuterium does not show a significant x dependence in the measured range of Q 2 and its Q 2 dependence is linear in log Q 2 . For calcium, a depletion of F 2 is observed at low x by 30% as compared with the values at x = 0.1 where F 2 (Ca) and F 2 (D) are not significantly different. This depletion is attributed to shadowing. The carbon structure function exhibits a similar, but less pronounced, x dependence. Such behaviour is observed to be independent of Q 2 . The data are consistent with those obtained from other charged lepton experiments both at similar and higher values of x and Q 2 and considerably extend the range of the measurements down to the low values of x to be measured in forthcoming experiments at HERA.
Carbon data. Overall normalization error of 8 pct not included.
We report results on a precision measurement of the ratio R=σLσT in deep inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤10 (GeV/c)2. Our results show, for the first time, a clear falloff of R with increasing Q2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences RA−RD and the cross section ratio σAσD between Fe and Au nuclei and the deuteron. Our results for RA−RD are consistent with zero for all x, Q2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios σAσD from all recent experiments, at all x, Q2 values, are now in agreement.
No description provided.