Final data measured with the EMC forward spectrometer are presented on the production of forward charged hadrons in μp and μd scattering at incident beam energies between 100 and 280 GeV. The large statistic of 373 000 events allows a study of the semi-inclusive hadron production as a function ofz,pT2 and 〈pT2〉 in smallQ2,xBj andW bins. Charge multiplicity ratios and differences as a function ofz andxBj are given forp, d andn-targets. From the differences of charge multiplicities the ratio of the valence quark distributions of the protondv(x)/uv(x) is determined for the first time in charged lepton scattering. The Gronau et al. sum rule is tested, the measured sum being 0.31±0.06 stat. ±0.05 syst., compared with the theoretical expectation of 2/7≈0.286. The measured sum corresponds to an absolute value of the ratio of thed andu quark charge of 0.44±0.10 stat.±0.08 syst.
No description provided.
No description provided.
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We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035
No description provided.
No description provided.
No description provided.
Measurements of the cross section and forward-backward asymmetry for the reaction e + e − → μ + μ − using the DELPHI detector at LEP are presented. The data come from a scan around the Z 0 peak at seven centre of mass energies, giving a sample of 3858 events in the polar angle region 22° < θ < 158°. From a fit to the cross section for 43° < θ < 137°, a polar angle region for which the absolute efficiency has been determined, the square root of the product of the Z 0 → e + e − and Z 0 → μ + μ − partial widths is determined to be (Γ e Γ μ ) 1 2 = 85.0 ± 0.9( stat. ) ± 0.8( syst. ) MeV . From this measurement of the partial width, the value of the effective weak mixing angle is determined to be sin 2 ( θ w ) = 0.2267 ± 0.0037 . The ratio of the hadronic to muon pair partial widths is found to be Γ h / Γ μ = 19.89 ± 0.40(stat.) ± 0.19(syst.). The forward-backward asymmetry at the resonance peak energy E CMS = 91.22 GeV is found to be A FB = 0.028 ± 0.020(stat.) ± 0.005(syst.). From a combined fit to the cross section and forward-backward asymmetry data, the products of the electron and muon vector and axial-vector coupling constants are determined to be V e V μ = 0.0024 ± 0.0015(stat.) ± 0.0004(syst.) and A e A μ = 0.253 ± 0.003(stat.) ± 0.003 (syst.). The results are in good agreement with the expectations of the minimal standard model.
Fully corrected cross sections.
Forward-backward asymmetries corrected to full solid angle, but not for cuts on momenta and acollinearity.
Effective weak mixing angle.
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Data is extrapolated to full x range.
Data requested from authors.
Quasi-elastic scattering with central dipion cluster production is studied in π+p andK+p interactions at 250 GeV/c. The cross section of double pomeron exchange is obtained as σDPE(π+p →π+(π+π−)p)=24 ±5 µb and σDPE(K+p→K+(π+π−)p)=19 ±5 µb. The low energy pomeron-pomeron cross section is estimated for the first time.
Numerical values supplied by W. Kittel.
Numerical values supplied by W. Kittel.
Numerical values supplied by W. Kittel.
In this paper an investigation of the production of D ∗ ± mesons produced in e + e − collisions at energies around the Z 0 pole is presented. Based on 115 D ∗ ± mesons with x D∗ 2E D ∗ /E cm > 0.2 the properties of D ∗ mesons produced in the reaction Z 0 → c c are studied. Fixing the yield and the fragmentation function of bottom quarks to the values obtained at LEP using lepton tags, and average energy fraction of the D ∗ ± mesons from primary charmed quarks of 〈x c → D ∗ 〉 = 0.52 ± 0.03 +- 0.01 is found and Γ z 0 →c c = (323 ± 61 ± 35) MeV is determined. The first error is the combined statistical and systematic error from this experiment, and the second the total error from other sources.
FD denotes the fraction of D* mesons from primary charmed quarks, derived from the fit (see text).
No description provided.
Using the ARGUS detector at thee+e− storage ring DORIS II at DESY, we have measured the inclusive production ofD0,D+ andD*(2010)+ mesons inB decays and in nonresonante+e− annihilation around 10.6 GeV. The inclusive branching ratios forB decays toD0,D+ andD*+ mesons are found to be (52.2±8.2±3.5)%, (27.2±6.3±3.5)% and (34.8±6.0±3.5)% respectively. Thus,D0 andD+ production account for about 70% of the charm produced inB decays, neglectingb→u contributions to the total width. The production cross sections and momentum spectra for continuume+e− annihilation are also presented.
Non-resonant inclusive cross sections.
Non-resonant inclusive cross sections.
Non-resonant inclusive cross sections.
None
DATA FROM 1989 RUN. The cross section are quoted with their statistical and point-to-point systematic uncertainty of both the multihadron acceptance and the luminosity calculation.
DATA FROM 1990 RUN. The cross section are quoted with their statistical and point-to-point systematic uncertainty of both the multihadron acceptance and the luminosity calculation.
Cross sections corrected for the effects of efficiency and kinematic cuts and background. Data from 1989 run, reanalysed.
We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S+W, O+W, andp+W reactions at 200 GeV/A around the target rapidity (y=1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope forp+W is much steeper than for O+W and S+W. The rapidity density forp+W is much higher than predicted by summing single nucleonnucleon collisions without any nuclear effects, indicating substantial rescattering of the produced particles. The predictions of the VENUS 3 model, including rescattering, show reasonable agreement with the data for all three systems. We do not have evidence for a strong collective flow of the outgoing particles.
No description provided.
No description provided.
No description provided.
From a sample of 150 000 hadronic Z decays collected with the ALEPH detector at LEP, events containing prompt leptons are used to measure the forward-backward asymmetries for the channels Z → b b and Z → c c , giving the results A FB b =0.126±0.028±0.012 and A FB c =0.064±0.039±0.030. These asymmetries correspond to the value of effective electroweak mixing angle at the Z mass sin 2 θ W ( m Z 2 ) = 0.2262±0.0053.
b asymmetry from high pt leptons.
b asymmetry from full pt range.
b asymmetry from full pt range.
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