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We report a measurement of the spin-dependent total cross section ratios ∆σ T / σ tot and ∆σ L / σ tot of the pp → ppπ 0 reaction between 325 MeV and 400 MeV. The experiment was carried out with a polarized internal target in a storage ring. Non-vertical beam polarization was obtained by the use of solenoidal spin rotators. Near threshold, the knowledge of both spin-dependent total cross sections is sufficient to deduce the strength of certain participating partial waves, free of any model. PACS numbers: 24.70.+s , 25.10.+s , 29.20.Dh , 20.25.Pj , 29.27.HjWe present a measurement of ∆σ T / σ tot and ∆σ L / σ tot for the pp → ppπ 0 reaction. The quantity ∆σ T (or ∆σ L ) equals the difference between the total cross sections measured with opposite and parallel, transverse (or longitudinal) beam and target polarizations, while σ tot is the (unpolarized) total cross section. At threshold a single partial wave ( 3 P 0 → 1 S 0 , l = 0) dominates. As the bombarding energy is increased other partial waves become significant. In the following, we will demonstrate how the results of the present experiment can be used to

We have measured the pp spin correlation coefficients A xx , A yy , A xz and the analyzing power A y at 250. 0, 280.0, 294.4, 310.0, 350.0, 399.1, and 448.9 MeV over the laboratory angular range 3.5°-43.5°( c.m. ϭ7°-90°). The statistical accuracy is approximately Ϯ0.006 for A y and Ϯ0.02 for A mn per 1°angle bin, while the corresponding scale factor uncertainties are 1.3 and 2.5 %, respectively. The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring ͑IUCF Cooler͒ and a circulating beam of polarized protons. The method of calibration relative to pp spin correlation coefficients and analyzing power at 197.4 MeV, the injection energy, involves up and down ramping of the energy of the polarized beam. The data are compared to recent pp partial waves analyses and NN potential models, emphasizing in particular the energy dependence in the region of the pion production threshold. ͓S0556-2813͑98͒01510-6͔

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