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1. chinaXiv:201609.01010 [pdf]

The nature of near-threshold XYZ states

Martin Cleven; Feng-Kun Guo; Christoph Hanhart; Qian Wang; Qiang Zhao
Subjects: Physics >> Nuclear Physics

We demonstrate that the recently observed X,Y,Z states cannot be purely from kinematic effect. Especially the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix which are qualified as states. We propose a way to distinguish cusp effects from genuine states and demonstrate that (not all of) the recently observed X,Y,Z states cannot be purely from kinematic effects. Especially, we show that the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix, since the normal kinematic cusp effect cannot produce that narrow structures in the elastic channels in contrast to genuine S-matrix poles. In addition, it is also discussed how spectra can be used to distinguish different scenarios proposed for the structure of those poles, such as hadro-quarkonia, tetraquarks and hadronic molecules. The basic tool employed is heavy quark spin symmetry.

submitted time 2016-09-14 Hits1270Downloads744 Comment 0

2. chinaXiv:201609.00927 [pdf]

Employing spin symmetry to disentangle different models for the XYZ states

Martin Cleven; Feng-Kun Guo; Christoph Hanhart; Qian Wang; Qiang Zhao
Subjects: Physics >> Nuclear Physics

In order to test different models proposed for some states discovered recently in the charmonium mass range that do not fit into the pattern predicted by the conventional quark model, we derive predictions for the spectrum within the hadro-charmonium picture, the tetraquark picture as well as the hadronic molecular approach. We exploit heavy quark spin symmetry for the hadro-charmonium and hadronic molecule scenarios. The patterns that emerge from the different models turn out to be quite distinct. For example, only within the hadro-charmonium picture a pseudoscalar state emerges that is lighter than the Y(4260). Possible discovery channels of these additional states are discussed.

submitted time 2016-09-13 Hits1441Downloads855 Comment 0

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