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The transverse spin correlations A x , x and A y , y in the n → p → → d π 0 reaction have been measured for the first time in quasi-free kinematics at the COSY-ANKE facility using a polarised deuteron beam incident on a polarised hydrogen cell target. The results obtained for neutron energies close to 353 MeV and 600 MeV are in good agreement with the partial wave analysis of data on the isospin-related p p → d π + reaction, though the present results cover kinematic regions that are largely absent from existing data sets.

In order to test chiral perturbation theory and establish links between p-wave pion production in nucleon–nucleon collisions and low energy three-nucleon scattering, an extensive programme of experiments on pion production is currently underway at COSY-ANKE. The final proton pair is measured at very low excitation energy, leading to an S-wave diproton, denoted here as {pp}s. By using a deuterium target we have obtained data on the differential cross section and analysing power of the quasi-free p→n→{pp}sπ− reaction at 353 MeV. The spectator proton psp was either measured directly in silicon tracking telescopes or reconstructed using the momentum of a detected π−. Both observables can be described in terms of s-, p-, and d-wave pion production amplitudes. Taken together with the analogous data on the p→p→{pp}sπ0 reaction, full partial wave decompositions of both processes were carried out.

The pp → ppϕ and quasi–free pn → dϕ reactions have been studied at the Cooler Synchrotron COSY–Jülich, using the internal beam and the ANKE facility. Total cross sections in the pp entrance channel have been determined at three excess energies ∊ in the range of 18.5–75.9 MeV. In case of the pn entrance channel the energy dependence of the cross section up to 80 MeV has been extracted by exploiting the intrinsic momentum of the neutron inside a deuterium target. Taken together with data for ω–production, a significant enhancement of the ϕ/ω ratio for both entrance channels of a factor 8 is found compared to predictions based on the Okubo–Zweig–Iizuka rule.

A study of the deuteron breakup reaction $pd \to (pp)n$ with forward emission of a fast proton pair with small excitation energy $E_{pp}, Comment: 17 pages including 6 figures and 1 table v2: minor changes; v3: minor change of author list; v4: changes in accordance with referee remarks

The transverse spin correlations ${A}_{x,x}$ and ${A}_{y,y}$ have been measured in the $\stackrel{P\vec}{d}\stackrel{P\vec}{p}\ensuremath{\rightarrow}{p}_{\text{spec}}{{pp}}_{s}{\ensuremath{\pi}}^{\ensuremath{-}}$ reaction at COSY-ANKE at 353 MeV per nucleon. Here ${{pp}}_{s}$ denotes a proton-proton pair with low excitation energy, which is dominantly in the ${}^{1}{S}_{0}$ state. By measuring three protons in the final state it was possible to extract events where there was a spectator proton ${p}_{\text{spec}}$ so that the reaction could be interpreted in terms of quasifree $\stackrel{P\vec}{n}\phantom{\rule{0.16em}{0ex}}\stackrel{P\vec}{p}\ensuremath{\rightarrow}{{pp}}_{s}{\ensuremath{\pi}}^{\ensuremath{-}}$. The proton and neutron analyzing powers in this reaction were also deduced from this data set by averaging over the polarizations of the deuteron beam and hydrogen target, respectively. The values of ${A}_{y}$ were shown to be consistent with a refined analysis of our earlier results obtained with a polarized proton incident on a deuterium target. Taking these data in combination with our previous measurements of the differential cross sections and analyzing powers in the $\stackrel{P\vec}{p}p\ensuremath{\rightarrow}{{pp}}_{s\phantom{\rule{0.16em}{0ex}}}{\ensuremath{\pi}}^{0}$ reaction, a more robust partial wave decomposition was achieved. Three different acceptable solutions were found, and the only way of resolving this ambiguity without further theoretical input would be through a measurement of the mixed spin-correlation parameter ${A}_{x,z}$.

Measurements of the pd{yields}p{sub sp}dK{sup +}K{sup -} reaction, where p{sub sp} is a spectator proton, have been undertaken at the Cooler Synchrotron COSY-Juelich by detecting a fast deuteron in coincidence with a K{sup +}K{sup -} pair in the ANKE facility. Although the proton beam energy was fixed, the moving target neutron allowed values of the nonresonant quasifree pn{yields}dK{sup +}K{sup -} total cross section to be deduced up to an excess energy {epsilon}{approx_equal}100 MeV. Evidence is found for the effects of K{sup -}d and KK final state interactions. The comparison of these data with those of pp{yields}ppK{sup +}K{sup -} and pp{yields}dK{sup +}K{sup 0} shows that all the total cross sections are very similar in magnitude.

At the ANKE facility of COSY Julich, the reactions pp→ppφ and pn→dφ have been investigated. Data for the total cross section in the pp entrance channel have been obtained at excess energies of 19 MeV, 35 MeV and 76 MeV. In case of the pn entrance channel the energy dependence of the cross section up to 80 MeV has been extracted by exploiting the intrinsic momentum of the target neutron using a deuterium target. The new φ data combined with the existing data on ω‐meson production provides the φ/ω production ratio in both, the pp‐ and pn‐channels. The ratios of both channels are found to be similar and about eight times larger than the ratio based on Okubo‐Zweig‐Iizuka (OZI) rule.

Vector and tensor analysing powers of the d(pol)p->(pp)n (charge-exchange) and d(pol)p->(pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A_xx and A_yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction., 10 pages, 4 figures

A kinematically complete study of the pd ? (pp)sn reaction with forward emission of an S-wave proton pair (pp)s has been performed at six beam energies 0.6, 0.7, 0.8, 0.95, 1.35 and 1.9 GeV. The experiment was carried out at the ANKE spectrometer installed at the internal beam of the proton synchrotron COSY (J?lich). The 3-momenta of both final state protons have been measured and events with a relative proton energy less than 3 MeV were selected as 1S0 diprotons. The differential cross sections of such pair production averaged over the c.m. polar angle of the total momentum of the pair in the range 0??8.1? have been obtained. A comparison of the result with a theoretical model based on the mechanism of pd-backward elastic scattering is described as well.

The vector and tensor polarizations of a deuteron beam have been measured using elastic deuteron-carbon scattering at 75.6 MeV and deuteron-proton scattering at 270 MeV. After acceleration to 1170 MeV inside the COSY ring, the polarizations of the deuterons were checked by studying a variety of nuclear reactions using a cluster target at the ANKE magnet spectrometer placed at an internal target position of the storage ring. All these measurements were consistent with the absence of depolarization during acceleration and provide a number of secondary standards that can be used in subsequent experiments at the facility., Comment: 12 pages, 13 figures

Values of the proton analysing power in the $pd\to{}^{3}\textrm{He}\,\pi^0/^{3}\textrm{H}\,\pi^+$ reactions at 350-360~MeV per nucleon were obtained by using a polarised proton beam incident on a deuterium cluster-jet target and with a polarised deuteron beam incident on a target cell filled with polarised hydrogen. These results have a much larger angular coverage than existing data. First measurements are also presented of the deuteron vector analysing power and the deuteron-proton spin correlations. Data were also obtained on the deuteron-proton spin correlation and proton analysing power at small angles at 600~MeV per nucleon, though the angular coverage at this energy was much more restricted even when using a deuteron beam. By combining the extrapolated values of the spin correlations to the forward or backward directions with published measurements of the deuteron tensor analysing powers, the relative phases between the two non-vanishing amplitudes were evaluated., Comment: 5 pages, 5 figures