The final results from the WA 1/2 neutrino experiment in the 1984 CERN 160 GeV narrow band beam are presented. The ratiosRν and\(R_{\bar v} \) of neutral to charged current interaction rates of neutrinos and antineutrinos in iron are measured to beRν=0.3072±0.0033 and\(R_{\bar v} \)=0.382±0.016. A value of the electroweak parameter sin2 θw = 1 −mW2/mZ2 is extracted fromRν. The result is sin2 θw =0.228+0.013(mc−1.5)±0.0003 (theor.) wheremc is the mass of the charmed quark in GeV formt=60 GeV,MH=100 GeV, ρ=1. CombiningRν and\(R_{\bar v} \) one obtains a value for ρ=0.991+0.023(mc−1.5)±0.020(exp.). Alternatively,Rν and\(R_{\bar v} \) yield a precise value of the ratio of intermediate vector boson massesmW/mZ=0.880−0.007(mc−1.5)±0.002(exp.)±0.002(theor.). Comparison of these results with those from direct measurements of the vector boson masses are presented. In a model-independent analysis the left- and right-handed neutral current coupling constants,gL2 andgR2, are determined.
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The spin asymmetry in deep inelastic scattering of longitudinally polarised muons by longitudinally polarised protons has been measured in the range 0.01<×<0.7. The spin dependent structure function g 1 ( x ) for the proton has been determined and, combining the data with earlier SLAC measurements, its integral over x found to be 0.126±0.010(stat.)±0.015(syst.), in disagreement with the Ellis-Jaffe sum rule. Assuming the validity of the Biorken sum rule, this result implies a significant negative value for the integral of g 1 for the neutron. These integrals lead to the conclusion, in the naïve quark parton model, that the total quark spin constitutes a rather small fraction of the spin of the nucleon. Results are also presented on the asymmetries in inclusive hadron production which are consistent with the above picture.
THE MEAN Q**2 FOR EACH OF THE 10 VALUES OF X BELOW ARE 3.5,4.5,6.0, 8.010.3,12.9,15.2,18.0,22.5,29.5.
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We present results on a high statistics study of the proton structure functions F 2 ( x , Q 2 ) and R = σ L / σ T measured in deep inelastic scattering of muons on a hydrogen target. The analysis is based on 1.8 × 10 6 events after all cuts, recorded at beam energies of 100, 120, 200 and 280 GeV and covering a kinematic range 0.06 ⩽ x ⩽ 0.80 and 7 GeV 2 ⩽ Q 2 ⩽260 GeV 2 . At small x , we find R to be different from zero in agreement with predictions of perturbative QCD.
THE AVERAGE VALUES OF Q**2 AT EACH OF THE X VALUES LISTED IN THIS TABLE ARE 15,20,20,25,30,35,40,45,50,50.
R=SIG(L)/SIG(T) IS TAKEN TO BE ZERO.
R=SIG(L)/SIG(T) IS TAKEN TO BE ZERO.
A new determination of the u valence quark distribution function in the proton is obtained from the analysis of identified charged pions, kaons, protons and antiprotons produced in muon-proton and muon-deuteron scattering. The comparison with results obtained in inclusive deep inelastic lepton-nucleon scattering provides a further test of the quark-parton model. The u quark fragmentation functions into positive and negative pions, kaons, protons and antiprotons are also measured.
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We report new results on a precision measurement of the ratio R=σLσT and the structure function F2 for 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 and F2 results are in good agreement with QCD predictions only when corrections for target-mass effects are included.
2.6 pct rad length target.
2.6 pct rad length target.
2.6 pct rad length target.
Using the CHARM detector 36 000 deep inelastic neutral-current reactions of neutrinos (and 2000 of antineutrinos) from the 160 GeV narrow-band beam were recorded. The differential cross section d σ d x in the Bjorken scaling variable x was computed by unfolding the effects of limited acceptance and of resolution of the detector as well as the ambiguity of the energy of the incoming neutrinos (produced by π- or K-decay). Combining the results from the neutrino and antineutrino data, the structure functions F 2 and xF 3 and the antiquark momentum distribution measured via the NC coupling were determined. The distributions are in agreement with the corresponding CC distibutions. Comparisons with deep inelastic muon scattering confirm the universality of nuclear structure functions as probed by the weak and the electromagnetic currents.
SEE THE PAPER FOR THE PRECISE DEFNS OF F(+), F(-).
Results are presented on the ratio of the inelastic muon-nucleus cross section per nucleon for carbon and calcium relative to that for deuterium. The measurements were made in the kinematic range of low x (0.003–0.1) and low Q 2 (0.3–3.2 GeV 2 ) at an incident muon energy of 280 GeV. The calcium to deuterium ratio shows a significant x dependence which is interpreted as a shadowing effect. No strong Q 2 dependence is observed. This suggests that the effect is due at least partially to parton interactions within the nucleus.
VALUES OF Q**2 AT EACH POINT ARE:- 0.52,0.60,0.61,0.61,0.63,0.68,0.90.
VALUES OF Q**2 AT EACH POINT ARE:- 1.09,1.25,1.54,1.74,1.76,1.68,1.71, 2.29.
VALUES OF X AT EACH POINT ARE:- 0.009,0.011,0.010,0.010,0.010,0.011, 0.013,0.015.
The inclusive yield of photons has been measured from deep inelastic interactions of 200 GeV muons on hydrogen. After subtracting the contributions from hadron electromagnetic decays and Bethe-Heitler muon bremsstrahlung, residual photons are observed at low p T and low z at a mean level of 0.15±0.06 per interaction. The quark Compton scattering process is unable to explain the data, thus indicating an anomalous photon production.
Z distribution of anomalous direct photons.
PT distribution of anomalous direct photons.
We measured the differences in R=σLσT and the cross-section ratio σAσD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤5 (Gev/c)2. Our results for RA−RD are consistent with zero for all x and 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 European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q2, are now in agreement.
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We have found 122 charmed-particle decays among 3855 neutrino interactions located in the fiducial volume of a hybrid emulsion spectrometer installed in the Fermilab wide-band neutrino beam. We obtain an average relative charmed-particle production cross section of σ(ν μ → c μ − ) σ(ν μ →μ − ) =4.9 −0.6 +0.7 % , at an average neutrino energy of 22 GeV. We also obtain a production rate of σ(ν μ → c c ν μ ) σ(ν μ →ν μ ) =0.13 −0.11 +0.31 % , if we assume that there was an undetected muon, a limit of σ(ν μ → c c μ − ) σ(ν μ → c μ − )<3% (90% CL ) can be obtained. Other cross section ratios and limits are also presented.
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