Speaker
Vadim Baru
(Ruhr University Bochum)
Description
Heavy quark spin symmetry (HQSS) partners of the X(3872) 1++ molecule are discussed in a coupled-channel approach with non-perturbative pions. In the strict heavy-quark limit the 1++ molecular state has three degenerate partner states with the 1+-, 0++ and 2++ quantum numbers. In the presence of pions this result is shown to be correct only if all allowed coupled-channel transitions between the DD, DD* and D*D* channels governed by the one-pion exchange potential are included. On the contrary, neglecting some of the coupled-channel transitions leads to a severe violation of HQSS and yields regulator-dependent results for the partner states. Deviations from the heavy-quark limit predictions are investigated for the 2++ partner state of the X(3872).
