Measurements of complete angular distributions of elastic K + p scattering at closely spaced incident momenta from 1368 to 2259 MeV/ c are presented and discussed. A PDP-8 computer controlled system of scintillation counters and core-readout wire spark chambers was used for the detection of elastic events. Diffractive behaviour is already present at the lowest measured momentum and becomes more prominent as the incident momentum increases. An expansion of the angular distributions in terms of Legendre polynomials shows no marked structure of the expansion coefficients as functions of the incident momentum. Our measurements can be adequately described by a number of existing phase shift solutions within 5% of their published values. Also Regge pole extrapolations represent our data satisfactorily.
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Differential cross sections for elastic scattering of negative kaons on protons are presented for 13 incident laboratory momenta between 1094 MeV/c and 1377 MeV/c. The data show the characteristic forward diffraction-like peak and backward dip and are adequately described in shape by certain published partial-wave analyses of the N system.
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Differential cross sections for elastic scattering of negative pions on protons are presented for 16 momenta between 996 MeV/ c and 1342 MeV/ c . The cross sections are compared with the predictions from published phase-shift analyses.
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Differential cross sections for the elastic scattering of negative kaons on protons are presented for 19 momenta between 1.732 GeV/ c and 2.466 GeV/ c . The general features of the cross sections are discussed.
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The total cross section for photoproduction of hadrons on the deutron, σ T d , has been measured for photon energies in the range 0.265–40215 GeV. From this, using results for the photon total cross section, obtained previously with the same apparatus, the neutron total cross section has been determined in the resonance region. The resonant structure is found to be quite different from that for the proton. Thereafter the neutron cross section falls off steadily with energy, and the values obtained are consistently lower than those for the proton. Forward scattering amplitudes have been evaluated for the deuteron.
RESONANCE REGION. UNSMEARING CORRECTION APPLIED, GLAUBER CORRECTION NEGLIGIBLE.
HIGHER ENERGY CROSS SECTIONS, IN 200 MEV BINS. OVERALL 3 PCT SYSTEMATIC ERROR IN ADDITION TO QUOTED STATISTICAL ERRORS. NEUTRON/PROTON CROSS SECTION RATIO HAS MEAN VALUE OF 0.94 +- 0.01.
SPIN AVERAGED FORWARD COMPTON SCATTERING AMPLITUDE. IM(AMP) WAS CALCULATED VIA THE OPTICAL THEOREM FROM A SMOOTH FIT TO THE DATA AND RE(AMP) WAS CALCULATED USING THE FORWARD DISPERSION RELATION. THE ESTIMATE OF -1.7 MUB*GEV FOR THE FIXED POLE CONTRIBUTION IS COMPARABLE WITH THE THOMPSON THRESHOLD AMPLITUDE OF -3 MUB*GEV.
The total cross section of γ rays in hydrogen resulting in hadron production, σT, has been measured over the energy range 265-4215 MeV. A tagging system with narrow energy bins was employed. Structure in the resonance region followed by a steady fall with energy has been observed and the results are analyzed. The forward amplitude of γ-proton scattering is evaluated, and its behavior in the Argand diagram studied as a function of energy. The relationships of the measurements to Regge-pole theory and the vector-dominance model are detailed.
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SPIN AVERAGED FORWARD COMPTON SCATTERING AMPLITUDE. IM(AMP) WAS CALCULATED VIA THE OPTICAL THEOREM FROM A SMOOTH FIT TO THE DATA, AND USED IN THE DISPERSION RELATION TO CALCULATE RE(AMP). AT THRESHOLD THE THOMSON AMPLITUDE IS -3.0 MUB*GEV.
During the LEP running periods in 1990 and 1991 DELPHI has accumulated approximately 450 000 Z 0 decays into hadrons and charged leptons. The increased event statistics coupled with improved analysis techniques and improved knowledge of the LEP beam energies permit significantly better measurements of the mass and width of the Z 0 resonance. Model independent fits to the cross sections and leptonic forward- backward asymmetries yield the following Z 0 parameters: the mass and total width M Z = 91.187 ± 0.009 GeV, Γ Z = 2.486 ± 0.012 GeV, the hadronicf and leptonic partials widths Γ had = 1.725 ± 0.012 GeV, Γ ℓ = 83.01 ± 0.52 MeV, the invisible width Γ inv = 512 ± 10 MeV, the ratio of hadronic to leptonic partial widths R ℓ = 20.78 ± 0.15, and the Born level hadronic peak cross section σ 0 = 40.90 ± 0.28 nb. Using these results and the value of α s determined from DELPHI data, the number of light neutrino species is determined to be 3.08 ± 0.05. The individual leptonic widths are found to be: Γ e = 82.93 ± 0.70 MeV, Γ μ = 83.20 ± 1.11 MeV and Γ τ = 82.89 ± 1.31 MeV. Using the measured leptonic forward-backward asymmetries and assuming lepton universality, the squared vector and axial-vector couplings of the Z 0 to charged leptons are found to be g V ℓ 2 = (1.47 ± 0.51) × 10 −3 and g A ℓ 2 = 0.2483 ± 0.0016. A full Standard Model fit to the data yields a value of the top mass m t = 115 −82 +52 (expt.) −24 +52 (Higgs) GeV, corresponding to a value of the weak mixing angle sin 2 θ eff lept = 0.2339±0.0015 (expt.) −0.0004 +0.0001 (Higgs). Values are obtained for the variables S and T , or ϵ 1 and ϵ 3 which parameterize electroweak loop effects.
Hadronic cross sections from the 1990 data set. Additional systematic uncertainties come from efficiencies and background of 0.4 pct in addition to the luminosity uncertainty 0.7 pct.
Hadronic cross sections from the 1991 data set. Additional systematic uncertainties come from efficiencies and background of 0.2 pct in addition to the luminosity uncertainty 0.6 pct.
E+ E- cross sections from the 1990 data set for both final state fermions in the polar angle range 44 to 136 degrees and accollinearity < 10 degrees (the s + t data).
We have measured the asymmetry parameter A and the spin correlation parameter A nn in pp elastic scattering, using the Argonne ZGS polarized proton beam and a polarized proton target. Angular distributions of A and A nn for | t | ≳ 0.2 (GeV/ c ) 2 were obtained at eight momenta between 1.10 and 2 if 2.75 GeV/ c . We find significant structure in both the energy and t -dependence of A nn at these energies. At p lab ≈ 1.34 GeV/ c A nn reaches a very large value of about 0.8–0.9 near θ cm = 90°.
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The real-to-imaginary ratio of the p p forward elastic scattering amplitude has been measured at the LEAR facility of CERN by the Coulomb-nuclear interference method at seven beam momenta between 181 and 590 MeV/ c . The ratio is positive at 590 MeV/ c , becomes negative below 500 MeV/ c , reaches a minimum at 260 MeV/ c and then crosses zero again at about 230 MeV/ c .
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The elastic cross section for proton proton scattering at 11.75 GeV/ c was measured at the Argonne ZGS using a 50% polarized target. In the range p ⊥ 2 =0.6 → 2.2 (GeV/ c ) 2 we obtained precise measurements of d σ d t(ij) for the ⇈ ⇊, and ⇅ initial spin states perpendicular to the scattering plane. We confirmed that the asymmetry parameter, A , decreases with energy in the diffraction peak, but is approximately energy-independent at large p ⊥ 2 . We found that the spin correlation parameter c nn acquires rather dramatic structure, and at large p ⊥ 2 seems to grow with energy.
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