Proton-proton spin correlations at charm threshold and quarkonium bound to nuclei

The anomalous behavior of the spin-spin correlation at large momentum transfer in $\mathrm{pp}$ elastic scattering is described in terms of the degrees of freedom associated with the onset of the charm threshold. A nonperturbative analysis based on the symmetries of QCD is used to extract the relevant dynamics of the charmonium-proton interaction. The enhancement to $\mathrm{pp}$ amplitudes and their phase follow from analyticity and unitarity, giving a plausible explanation of the spin anomaly. The interaction between $c\overline{c}$ and light quarks in nuclei may form a distinct kind of nuclear matter: nuclear bound quarkonium.