We have measured ρ, the ratio of the real to the imaginary part of the p¯p forward elastic-scattering amplitude, at √s =1.8 TeV. Our result, ρ=0.140±0.069, is compared with extrapolations from lower-energy data based on dispersion relations, and with the UA4 value at √s =546 GeV.
Results of least square's fit to the distribution.
Total cross section from fit to data.
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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AVERAGED DATA FOR 44.9 AND 45.5 GEV.
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The differential cross sections for KL0p→KS0p scattering are presented in several momentum intervals between 1 and 10 GeVc. The data are strongly peaked in the forward direction, characteristic of a large s-channel helicity-nonflip scattering amplitude in this reaction, and a distinct break in the differential cross section occurs at |t|=0.3 GeV2. The phase of the forward scattering amplitude, φ, is consistent with being independent of momentum. The average value of the phase, φ=−133.9±4.0∘, corresponds to a Regge trajectory α(0)=0.49±0.05 in agreement with the canonical ρ, ω0 Regge intercept, α(0)∼0.5. However, this result disagrees with the Regge trajectory determined from the energy dependence of the forward cross section, α(0)=0.30±0.03, indicating a breaking of the Regge phase-energy relation. Comparisons of KL0p→KS0p and π−p→π0n scattering data reveal substantial differences in the energy dependence of the differential cross sections. Comparisons to KN charge-exchange data then suggest that direct-channel (absorption) effects may explain the differences in πN and KN channels.
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Proton-proton elastic scattering has been measured over the four-momentum transfer squared 0.0007 ⩽ t ⩽ 0.02 GeV 2 /c 2 . A gas hydrogen jet has been used as an internal target of the accelerator. The results indicate that the ratio of the real to the imaginary part of the proton-proton forward scattering amplitude rises smoothly with increasing energy from α = −0.35 ± 0.05 at p = 9.39 GeV/ c to α = −0.092 ± 0.011 at p = 69.8 GeV/ c .
THE TOTAL ELASTIC CROSS SECTION IS DERIVED FROM THE OPTICAL THEOREM POINT AND SLOPE PARAMETER.
K + p elastic scattering is studied at incident K + beam momenta of 2.53, 2.76 and 3.20 GeV/ c . From the analysis of about 10 000 elastic events at each energy, we present data on the forward and backward elastic scattering peaks. No structure is observed in the forward peak for − t ⩽ 2 (GeV/ c ) 2 . In addition, the statistics available from this exposure permit a measurement of the differential cross sections near 90° in the center of mass system. These results exhibit a strong energy dependence and are compared to similar results at other energies.
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THE QUOTED ERRORS ARE STATISTICAL.
A study of elastic scattering, one-pion production and annihilation reactions in p p interactions at 5.7 GeV/ c was carried out, from the two-prong events, obtained in the hydrogen bubble chamber exposed at CERN.
NUMBER OF EVENTS FOR -T<0.03 GEV**2 CALCULATED BY EXTRAPOLATION.
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