Measurements of the spin observables ANN(90∘) and AN0(90∘) for the reaction pp→dπ+ between 500 and 800 MeV are presented and compared with previous measurements and with predictions from theories and a partial-wave analysis. These are the first available measurements of ANN above 590 MeV.
ANALYSING POWER IS POL.POL(NAME=AN0).
The spin-spin correlation parameters CLL=(L,L;0,0)=ALL and CSL=(S,L;0,0)=ASL for np elastic scattering were measured for incident polarized-neutron–beam kinetic energies of 484 and 634 MeV over the center-of-mass angles from ≃80° to 180°. The data are important for determining the I=0 nucleon-nucleon amplitudes. These results are compared with phase-shift calculations.
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The energy dependence of the analyzing power A y for the pp → π + d reaction was measured during polarized beam acceleration from 500 to 800 MeV, using an internal target inserted into the beam every acceleration cycle. The measurements were made with the pion laboratory angle fixed at 68° and with incident proton energy bins varying from 10 to 30 MeV in width. The statistical accuracy per bin is ΔA y ⋍ 0.06 .
Statistical errors onnly.
The energy dependence of the pp elastic analyzing power has been measured using an internal target during polarized beam acceleration. The data were obtained in incident-energy steps varying from 4 to 17 MeV over an energy range from 0.5 to 2.0 GeV. The statistical uncertainty of the analyzing power is typically less than 0.01. A narrow structure is observed around 2.17 GeV in the two-proton invariant mass distribution. A possible explanation for the structure with narrow resonances is discussed.
Statistical errors only.
Angular distributions of the spin-correlation parameters Asl and All for the reaction pp→π+d have been measured at pion center-of-mass angles 40°≤θπ+*≤130° at incident energies of 500, 650, and 800 MeV. Additional measurements of All were made at 600, 700, and 750 MeV. The results of the experiment are compared with the predictions of several unified coupled-channel calculations and partial-wave analyses. While the latest partial-wave analyses were found to fit the data reasonably well, all except one of the various model predictions not only do not fit the data well, but also tend to be in disagreement with each other. The data show no clear sign of a need for proposed dibaryon resonances.
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The cross section for elastic scattering of 794-MeV neutrons by deuterium has been measured for neutron center of mass angles from 139° to 179°. The angular distribution is fitted very well both by an empirical function αeβ(μ−μ180∘) and by a calculation that uses the one parameter Craigie-Wilkin triangle diagram technique. [NUCLEAR REACTION nH2→H2n, E=794 MeV; measured σ(θ). Calculated σ(θ) with triangle diagram techniques.]
X ERROR H = 12.60 CM. X ERROR D(THETA) = 2.0000 DEG.
The analyzing power A and spin-transfer parameters KNN, KSS, KSL, and KLL have been measured in the np charge-exchange (np→pn) region at 790 MeV. These data provide new and unique information on the spin dependence of the np interaction in the charge-exchange region. Models which explain the charge-exchange peak in the np elastic differential cross section as being due to interference between one-pion exchange and a slowly varying background are in basic agreement with the data.
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USING PHASE-SHIFT VALUES FOR KLS AND KSL.
pp-elastic differential cross sections are reported at 492 MeV from 40° to 90°, and at 576, 642, 728, and 793 MeV from 75° to 90° c.m., with an absolute accuracy of less than 1%. These data, obtained with polyethylene targets, agree with recent measurements at the same energies obtained with a liquid-hydrogen target. © 1996 The American Physical Society.
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The differential cross section for n-p elastic scattering at 459 MeV in the c.m. angular region 50°<θ*<180° has been measured with high statistical precision and good relative accuracy. The uncertainty in the absolute normalization (based on the simultaneously measured yield of deuterons from the np→dπ0 reaction) was initially estimated to be ∼7%. The results agree well with back-angle data obtained independently at LAMPF but less well with results from Saclay and the Princeton-Pennsylvania Accelerator and, except for a normalization difference of 10%, are fairly well represented by a phase-shift fit. The pole-extrapolation method of Chew was used to extract the pion-nucleon coupling constant f2 from the back-angle portion of the data. The value obtained, f2=0.069, is somewhat smaller than the values 0.0735–0.0790 obtained from analyses of pion-nucleon scattering, tending to confirm the need for an upward renormalization of the angular distribution by ∼10%.
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Absolute pp-elastic-differential cross sections were measured at incident energies 492, 576, 642, 728, and 793 MeV from about 30° to 90° c.m. The total uncertainty was determined to be less than 1%, made possible by particle counting for beam normalization and extensive cross-checks of systematic effects. These new data are consistent with previous data above 600 MeV but have uncertainties about a factor of 10 smaller. Near 500 MeV these data are consistent with 90° data from TRIUMF, but differ significantly from similar data from PSI; the cause of this discrepancy is discussed.
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