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The mixed spin-spin correlation parameter Cσσ≈0.5CSS−0.8CSL for np elastic scattering was measured for incident-neutron-beam kinetic energies of 484, 634, and 788 MeV over the center-of-mass angular range 75°-180°. These Cσσ data are important for determining the I=0 nucleon-nucleon amplitudes and provide strong constraints on the phase-shift solutions. It was found that the P11, S13, and D13 isospin-0 partial waves are most strongly affected.
Mixed spin parameter POL.POL(NAME=CXX) is given by 0.475 * CSS + 0.088 CNN + 0.1390 CLL - 0.744 CSL.
Mixed spin parameter POL.POL(NAME=CXX) is given by 0.506 * CSS + 0.064 CNN + 0.163 CLL - 0.809 CSL.
Mixed spin parameter POL.POL(NAME=CXX) is given by 0.528 * CSS + 0.050 CNN + 0.178 CLL - 0.824 CSL.
The spin-correlation parameter Ann for free n-p elastic scattering has been measured for the first time for incident-neutron-beam energy En=790 MeV and c.m. angles 48°≤θ*≤149°. The data are compared with the widely differing predictions of several phase-shift analyses, clearly favoring one of them. They also are compared with recently published quasifree Ann data for the more limited c.m. angular region 98°≲θ*≲122°.
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Data on the reactions (K+/π+)p→(K+/π+)pπ+π- and (K+/π+)p→(K+/π+)p2π+2π-, obtained with the European Hybrid Spectrometer, are presented and compared with data at lower energies. The contribution of beam and target diffractive dissociation and double Pomeron exchange, and porperties of these reactions are discussed.
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This paper describes measurements of the semileptonic weak-neutral-current reactions νpμ→νpμ and ν¯pμ→ν¯pμ which yield the absolute differential cross sections dσ(νpμ)dQ2 and dσ(ν¯pμ)dQ2. The weak-neutral-current parameter, sin2θW, is determined to be sin2θW=0.220±0.016(stat.)(syst.)−0.031+0.023.
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The reaction γγ→π+π-π+π-π0 has been studied using the JADE detector at PETRA. The cross sections for γγ→ωπ+- and for γγ→ωρ0- are given. We observe no peak in these cross sections in the regionWγγ=1.9–2.0 GeV.
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We report on the properties of theZ resonance from 62 500Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We findMZ=(91.193±0.016exp±0.030LEP) GeV, ΓZ=(2497±31) MeV, σhad0=(41.86±0.66)nb, and for the partial widths Γinv=(489±24) MeV, Γhad(1754±27) MeV, Γee=(85.0±1.6)MeV, Γμμ=(80.0±2.5) MeV, and Γττ=(81.3±2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Γu=(84.3±1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors,gv2(MZ2)=(0.12±0.12)×10−2 andgA2(MZ2)=0.2528±0.0040. The number of light neutrino species isNν=2.91±0.13; the electroweak mixing angle is sin2θW(MZ2)=0.2291±0.0040.
Hadronic cross section from the charged track selection trigger.
Hadronic cross section from the calorimeter selection trigger.
Averaged hadronic cross section.
We have measured the cross section for e + e − →hadrons over the center of mass energy range of the Z 0 peak, from 88.22 to 95.03 GeV. We determine the Z 0 mass M z =91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γ invisible =0.502±0.018 GeV, and the number of light neutrino species, N ν =3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e + e − →hadrons and e + e − → μ + μ − data to determine total width, leptonic width and hadronic width of the Z 0 .
Cross sections from 1990 data. Additional systematic error 1.5 pct.
Cross sections from 1989 data. This data has been rescaled by 0.96 from original publication PL B237 (90) 136. Additional systematic error 2.0 pct.
We present a study of jet multiplicities based on 37 000 hadronic Z 0 boson decays. From this data we determine the strong coupling constant α s =0.115±0.005 ( exp .) −0.010 +0.012 (theor.) to second order QCD at √ s =91.22GeV.
Errors are combined statistical and systematic uncertainties.
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