Differential cross sections for the exclusive reaction p⃗p→ppη observed via the η→π+π−π0 decay channel have been measured at Tbeam=2.15GeV, 2.50GeV, and 2.85GeV (excess energies 324MeV, 412MeV, and 554MeV). The influence of the N(1535)S11 resonance is clearly seen in the invariant mass and momentum dependent differential cross sections. The extracted resonance parameters are compatible with existing data. No significant evidence for further resonance contributions has been found. In addition, angular distributions of the ppη final state have been measured. The polar angle distribution of the η shows an anisotropy with respect to the beam axis for the lowest beam energy, which vanishes for the higher energies. The sign of this anisotropy is negative and expected to be sensitive to the dominant production mechanism. In contrast, the proton polar angle in the pp rest frame tends to be more strongly aligned along the beam axis with increasing beam energy. The analyzing power Ay is compatible with zero for all beam energies.
Differential cross section for incident kinetic energy 2.15 GeV, divided by the phase space as a function of the invariant mass of the ETA and the final state proton with the lower value of ABS(T). This is proportional to the square of the decay matrix element ABS(M)**2 of the P-ETA system.
Differential cross section for incident kinetic energy 2.50 GeV, divided by the phase space as a function of the invariant mass of the ETA and the final state proton with the lower value of ABS(T). This is proportional to the square of the decay matrix element ABS(M)**2 of the P-ETA system.
Differential cross section for incident kinetic energy 2.85 GeV, divided by the phase space as a function of the invariant mass of the ETA and the final state proton with the lower value of ABS(T). This is proportional to the square of the decay matrix element ABS(M)**2 of the P-ETA system.
Polarization parameters for the π − p → π 0 n charge exchange scattering have been measured at eight beam momenta between 1965 and 4220 MeV/ c using two different experimental set-ups. The angular range covered is −0.90 < cos θ π ∗ < 0.95 at the five momenta of 1965, 2168, 2360, 2566 and 2960 MeV/ c , where θ π ∗ is the emission angle of the π 0 meson in the c.m.s.. For three momenta of 2770, 3490 and 4220 MeV/ c , the measurements cover the forward angles of 0.1 < cos θ π ∗ < 1.0 . The results are compared with the predictions of π N partial wave analyses.
Polarisation measurements from SETUP1. Errors are statistical only.
Polarisation measurements from SETUP2. Errors are statistical only.
Legendre polynomial coefficients for fit to differential cross section data.
This paper presents the results of a study of the dominant neutral final states from π−p interactions. The data were obtained in an experiment performed at the Brookhaven National Laboratory Alternating Gradient Synchrotron, using a set of steel-plate optical spark chambers surrounding a liquid-hydrogen target. We present differential and total cross sections for the reactions (1) π−p→n+π0 and (2) π−p→n+η0(η0→2γ) and total cross sections for the reactions (3) π−p→n+kπ0 (k=2, 3, 4, and 5) and (4) π−p→all neutrals for eighteen values of beam momentum in the interval 1.3 to 4.0 GeV/c. The angular distributions for (1) and (2) have been analyzed in terms of expansions in Legendre polynomials, the coefficients for which are also given.
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SIG = 4*PI*LEG(L=0).
FORWARD DIFFERENTIAL CROSS SECTION CALCULATED FROM LEGENDRE POLYNOMIAL COEFFICIENTS AND ERROR MATRICES.
Elastic scattering of p¯ on p has been studied for cosθc.m. between -0.88 and -1.0 and Plab(p¯) between 0.70 and 2.16 GeV/c. The momentum dependence of the cross section shows a sharp dip at 0.9 GeV/c and a broad peaking around 1.4 GeV/c. The possibility of the peak resulting from direct formation of boson resonances has been studied. Alternatively, a diffraction model agrees qualitatively with our data and other elastic data at different angles.
'1'. '2'. '3'.
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