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The total cross sections σT of p, p¯, π±, and K± on hydrogen and deuterium have been measured between 6 and 22 GeVc at intervals of 2GeVc to an accuracy greater than previously reported. The method utilized was a conventional good-geometry transmission experiment with scintillation counters subtending various solid angles at targets of liquid H2 and D2. With the increase in statistical accuracy of the data, it was found that a previously adopted procedure of linearly extrapolating to zero solid angle the partial cross sections measured at finite solid angles was not a sufficiently accurate procedure from which to deduce σT. The particle-neutron cross sections are derived by applying the Glauber screening correction to the difference between the particle-deuteron and particle-proton cross sections. The cross sections σT(π+d) and σT(π−d) are equal at all measured momenta, which confirms the validity of charge symmetry up to 20GeVc. Results are presented showing the variation of cross sections with momentum; evidence is presented for a small but significant decrease in σT(pp) [and σT(pn)] in the momentum region above 12GeVc.
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The spin-spin correlation parameter CSS=(S,S;0,0) has been measured for p−p elastic scattering over a large angular range. The data are particularly useful in checking currently available phase-shift solutions.
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The elastic scattering of negative pions on protons at 2.26 GeVc has been studied using the Lawrence Radiation Laboratory 72-in. hydrogen-filled bubble chamber. The elastic scattering cross section is found to be 8.91±0.24 mb. The forward diffraction peak is well fitted by an exponential in the square of the four-momentum transfer, and the slope is found to be 8.8±0.1 GeV−2. The differential cross section is parametrized in terms of three models: optical, strong-absorption, and two-slope. It is found that the two-slope model affords the best description of the data and also does very well in predicting the polarization data of other experiments. The best-fit parameters for all three models are given. In addition, the amplitudes associated with the best fits are given for the strong-absorption and the two-slope models.
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We present an analysis of ππN final states obtained from π−p interactions at 2.26 GeV/c. Strong ρ production is present in both final states. In addition, significant nucleon isobar production is observed. We observed the following cross sections: σ(π−π0p)=3.77±0.13 mb, σ(π−π+n)=5.67±0.17 mb, σ(ρ−p)=2.19±0.09 mb, σ(Δ+(1236)π−)=0.30±0.10 mb, σ(N0(1650)π0)=0.49±0.07 mb, σ(ρ0n)=2.89±0.11 mb, σ(Δ−(1236)π+)=0.11±0.06 mb, σ(N+(1470)π−)=0.24±0.06 mb, and σ(N+(1650)π−)=0.45±0.05 mb. The spin-density matrix elements are determined for the ρ0 by interpreting the ρ0 asymmetry as an interference between the resonant P wave and a T=0 S wave. A search for the ε0 in the π+π−n final state failed to yield a direct observation of this effect.
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We have measured differential cross sections for both π+p and π−p elastic scattering at incident-pion kinetic energies of 30, 50, 70, and 90 MeV in the center-of-mass angular range between 50° and 150°. The experiment detected pions scattered from a liquid-hydrogen target with multiwire proportional chambers and scintillation-counter range telescopes. The relative accuracy of each angular distribution is better than 5%, while the absolute cross sections have uncertainties of 4% to 25%. Our results for the absolute cross section for π+p scattering at 30 and 90 MeV are inconsistent with previous measurements. Our π−p measurements comprise the first extensive set of precision differential cross sections below 90 MeV.
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The analyzing power A N of proton-proton, proton-hydrocarbon, and antiproton-hydrocarbon, scattering in the Coulomb-nuclear interference region has been measured using thhe 185 GeV/ c Fermilab polarized-proton and -antiproton beams. The results are found to be consistent with theoretical predictions within statistical uncertainties.
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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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Accelerating polarized protons to 22 GeV/c at the Brookhaven Alternating Gradient Synchro- tron required both extensive hardware modifications and a difficult commissioning process. We had to overcome 45 strong depolarizing resonances to maintain polarization up to 22 GeV/c in this strong-focusing synchrotron. At 18.5 GeV/c we measured the analyzing power A and the spin-spin correlation parameter Ann in large- P⊥2 proton-proton elastic scattering, using the polarized proton beam and a polarized proton target. We also obtained a high-precision measurement of A at P⊥2=0.3 (GeV/c)2 at 13.3 GeV/c. At 18.5 GeV/c we found that Ann=(-2±16)% at P⊥2=4.7 (GeV/c)2, where it was about 60% near 12 GeV at the Argonne Zero Gradient Synchrotron. This sharp change suggests that spin-spin forces may have a strong and unexpected energy dependence at high P⊥2.
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2.2 GeV point taken from Brown et al., PR D31(85) 3017.
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