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An analysis of the reaction pp --> ppηnear threshold

K. Nakayama·J. Haidenbauer·C. Hanhart·J. Speth
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Abstract

It is shown that most of the available data on the $pp\to ppη$ reaction, including the invariant mass distributions in the $pp\to ppη$ reaction recently measured at COSY, can be understood in terms of the partial-wave amplitudes involving final $pp$ $S$ and $P$ states and the $η$ meson s-wave. This finding, together with the fact that results within a meson--exchange model are especially sensitive to the details of the excitation mechanism of the $S_{11}(1535)$ resonance, demonstrates the possibility of investigating the properties of this resonance in $NN$ collisions. The spin correlation function $C_{xx}$ is shown to disentangle the $S$- and $P$-wave contributions. It is also argued that spin correlations may be used to help constrain the contributions of the amplitudes corresponding to the final $pp$ $^3P_0$

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K. Nakayama, J. Haidenbauer, C. Hanhart, J. Speth. 2003-11-13. An analysis of the reaction pp --> ppηnear threshold. https://doi.org/10.1103/physrevc.68.045201

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